diff --git a/10/a.py b/10/a.py
new file mode 100644
index 0000000..5e89a41
--- /dev/null
+++ b/10/a.py
@@ -0,0 +1,46 @@
+with open("input.txt") as f:
+    lines = [l.strip() for l in f.readlines()]
+
+
+pairs = {
+    "(": ")",
+    "[": "]",
+    "{": "}",
+    "<": ">",
+}
+
+antipairs = {
+    ")": "(",
+    "]": "[",
+    "}": "{",
+    ">": "<",
+}
+
+openers = set("([{<")
+closers = set(")]}>")
+
+scores = {
+    ")": 3,
+    "]": 57,
+    "}": 1197,
+    ">": 25137,
+}
+
+
+def process_line(line):
+    stack = []
+    for c in line:
+        if c in openers:
+            stack.append(c)
+        else:
+            x = stack.pop()
+            if antipairs[c] != x:
+                return scores[c]
+    return 0
+
+
+score = 0
+for line in lines:
+    score += process_line(line)
+
+print(score)
diff --git a/10/b.py b/10/b.py
new file mode 100644
index 0000000..edc9a33
--- /dev/null
+++ b/10/b.py
@@ -0,0 +1,66 @@
+with open("input.txt") as f:
+    lines = [l.strip() for l in f.readlines()]
+
+
+pairs = {
+    "(": ")",
+    "[": "]",
+    "{": "}",
+    "<": ">",
+}
+
+antipairs = {
+    ")": "(",
+    "]": "[",
+    "}": "{",
+    ">": "<",
+}
+
+openers = set("([{<")
+closers = set(")]}>")
+
+scores = {
+    ")": 1,
+    "]": 2,
+    "}": 3,
+    ">": 4,
+}
+
+
+def calc_score(chars):
+    score = 0
+    for c in chars:
+        score = score * 5
+        score += scores[pairs[c]]
+    return score
+
+
+def process_line(line):
+    stack = []
+    for c in line:
+        if c in openers:
+            stack.append(c)
+        else:
+            x = stack.pop()
+            if antipairs[c] != x:
+                return 0  # invalid line
+    stack.reverse()
+    return calc_score(stack)
+
+
+line_scores = []
+
+for line in lines:
+    s = process_line(line)
+    if s:
+        line_scores.append(s)
+
+
+line_scores.sort()
+
+print(line_scores)
+print(len(line_scores))
+
+print(line_scores[len(line_scores) // 2])
+
+# 22m
diff --git a/10/input.txt b/10/input.txt
new file mode 100644
index 0000000..ae1deb5
--- /dev/null
+++ b/10/input.txt
@@ -0,0 +1,98 @@
+[[{[<{{<<{<[<{<>[]}([][])>{{<>()}<()>}](({{}<>}[[]<>])<([]<>){[]()}>)>[<{{<>}<[]()>}[{[][]}<{}{}>]><{<
+{[<[({([[(<<(([]{}))<[{}()]>>>)]])<([<{[{({}{})[[]()]}[(()[])<{}()]]]{{[[][]]<<>[]>}}}{([([
+{<{<{(({[[([{<<><>>([]())}[{()[]}({}())]}<{{{}}{[]<>}}({<>{}})>){<(([]())([]<>))(<<>[]><[]<>>)>({[[]
+{[([<{<([{{(({()<>}({}<>)))(<{<>{}}](<<>[]><()()>))}{[{{[]()}(<>[])}{{[][]}{<>{}}}]}}{[{{{{}[]}<<>()>}}<{([]
+[({[{[(<<<[((<{}<>><{}{}>)({[]<>}((){}))){{[{}<>]{{}<>}}})[<[<<>>[<>{}]]{{<>[]}}>]>>[[([<{<><>}
+<[{[{[[<{[[{<<[]()>[{}<>]>}]<([{{}}({}{})])>]{<[[<<><>><()[]>]([[]<>]{[]<>})]{(([][]){()[]})
+((<(<(<[(<([(<{}<>>(()()))](<{{}[]}{()[]}>))<<<(<>[]){()()}>([<>{}]{{}})>({{[][]}(()())}(<
+{{([(<{<([([[[<><>][()<>]]{(()[])}])]({<[<<>>[()<>]]({()[]}[{}()])>]))>({<<[<{[]()}<<>[]>>{<[]
+([<{{((<({<[<({}<>)[[]()]>]([(<>)<(){}>](([][]){{}{}}))>{(({<>[]}<()()>){(()[])})[{{[][]}((){})}[([]<>)({}{})
+<<<{<{<([<[((<()<>]<[]()>)[(<>[])[{}<>]])]><[<[(()())[()()]]{[{}{}][()()]}>]{<<(<>())[<>[]]>>[<(()())<[]
+{<[[({<[{[{[({{}<>}<<>{}>){<{}[]><{}{}>}]{{<<>>}<(<>()){()<>}>}}]}{{<[({{}()})([()<>]{[]})
+(((([[(((<(<<(<>())[(){}]>([[][]]{()()})>{<[<>[]][()<>]>(([]{})[<>{}])})[({{()<>}({}())})]>([[[(()<>)][[<>()
+[<({([[[<<([<<<>()>>{[<>()](<>{})}]){<[[{}<>]]<{{}<>}([]{})>>}>[<<<{{}()}>>[[([][])<<><>>]({<>
+{<(<<{{<<[({{({}<>)[[][]]}(<()[]>[<>])}<{<()>{{}()}}>){{<[(){}][(){}>><{{}<>}[[]{}]>}}]<{<{
+{(<{<[<(<<(<[([][])<[]{}>]><{([]())(<>{})}{<(){}><[][]>}>><({({}[]){<>()}}{<{}>(())})>>{({{(<><>)[{}()]}
+[(<{[<<[{((({[{}<>][[]<>]}){(<{}<>>({}<>))<(<><>)[<>]>})<({{<>[]}}}>)}]>([{{<<{{[][]}(<>())}<{{}
+<<<[[{[<<{[{<(()[])<[]()>>}[(({}[]))(({}<>){<>})]](([{(){}}[<>]]<[{}{}]<{}<>>>))}>{{[(((()[]){(){}})(<(){}>{
+[{{<<([[[[<<[{(){}}{(){}}]{<{}()>(()())}>{{<{}()>}<[<><>][()()]>)>([{{()<>}<()[]>}[[<><>]{[]<>}]]{[{
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+{{{<{([[[<[<{{(){}}({}{})}>[[{()[]}<[]{}>]<<()<>>[()[]]>]}<{[[[]()]<<><>>]({<><>}<[][]>)}{(<[]()><{}<>>)}>>
+([<<[(([{{[([{<>{}}])<[(()){<>{}}]>](<{([][])[<>()]}<{{}()}>>)}>{[{{(<()()>[<><>])((<><>){()()})}{([[][]])[[{
+[{((({<([{(<{(<>)[[]()]}({{}<>}<[]<>>)>)}(<<[({}{})]{({}<>)[<>()]}>>[<[[()<>]{<>()}][<[][]><<>{}>]>[<([][])[(
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+<[{([<<(<(<[(({}()){[][]})[[(){}][[]()]]][<[{}]([][])>]>}>(<{[({[]<>}{(){}})<(<>)({}())>]<[({}<>)<{
+(({[{<({<<[<{{[]<>}[<><>]}{{{}}<()[]>}>]<<<{()()}{{}<>}>([[]()][<>()])>>><[([(<><>)<()[]>]
+{([<<[{[(({[{{()<>}({}{})}<[{}[]]<(){}>>]<{<[]<>>}<[()()][()()]>>}<<[[(){}](<><>)]><(<{}[]>
+{([<{<([(<(<(<[]{}>{<>()}){{<>{}}}>({<[][]>(<>{})}))<[<[{}{}]<{}{}>>{(<>[])(<>())}][<{{}<>}(()[]
+[{[(<(({{(<{(<[][]>){[<>{}]}}{<{(){}}{<><>}>({[]{}}{[]{}})}>)(<[(([]<>))[[[]()]<[]<>>]]<{({}[])<{}<>>}[
+[{<{({((<{[{[<<>{}>[[]]]{<{}()>[<>]}>]}>[{([(<[][]>{[]()}){<(){}>[<>[]]}][[([]<>)<[]{}>]{{{}}[{}]}])([
+{<(<({[{[(({((<>[])<{}{}>)({[]<>>[{}[]])}([{(){}}([])]{<<>[]>[{}()]}))[[<[<><>]<<><>>>{[()()]<
+{{{<[<<{(<(([({}<>)<()>]{<()()><[]<>>})(<[()[]]{[]{}}>{{{}{}}(<>())}))({([[]()]{()[]}){{{}<>}[
+(<({{[{<{[<[[{[]()}]([[]()][<>{}])][[[<>]{<>}]<([]{})<{}[]>>]>{[{{<><>}[[][]]}<{[]{}}({}())>](<[[]()]({
+<<[{[<{<[[(<[<(){}>(<>)](<[]<>>[[]()])>{<<{}[]><{}()>>[(()[])(<>{})]})({({{}<>}[<>{}])}{({[][]}<<><>>)})]({<[
+[[([<{{(<({[{([][])(()<>)}]{{{[]<>}[()()]}[({}{})[()[]]]}}>><[[{{[()()]({}())}}({(()[])[[]()]}{
+<<{(<(([{((<([()()]){{[]<>}{{}()}}>)<<<({}<>)[<>{}]><({}[])<[]<>>>>(<[[]]{(){}}>(([][])([])))>)[{[{([]<>)[<>{
+[(<(<<{{[([[[({}{})<()())]({[]}{{}[]})]({[()()]([]{})}{({}[])[[]()]})]<[[{<><>}<[][]>][[[]()]{(){}}]]>){(([<(
+[[<[<{<[{({{{{<>{}}<[]()>}<<(){}>>}<{{{}{}}{()<>}}[([]{}){<>{}})>})[[((<<><>>[{}[]])<{()<>}<()
+((<(<<[[{{{(<<{}()>[()()]><((){})>)[[[[][]][()[]]][{[]<>}<{}{}>]])((([[]{}]<[]{}>))([{<>{}}(<
+{{(({[{[({({<<<>[]><<>[]>>{{()[]}[{}()]}})[{(<{}<>><[]>)(({}[]){{}[]})}<<<[]()><[]{}>><{<><>}<()<>>>>]})
+[(<[{[<({{[{<[<>()]([]{})><{(){})[()[]]>}<(<()()>(()()))(<{}[]>({}[]))>]([([[]()]({}{}))({(){}}([](
+{({(({[<{<[<<{<><>}(<>[])>[<{}{}><[]<>>]><<{<>}>>](<<<()<>>(()<>)>{<{}[]>([]<>)>>)>}<{<{{<<
+<([[[(({[{<(({<>[]}<<>[]>){<{}[]>([]()))){<({}<>)<[][]>>{<{}{}>{()[]}}}>{((({}{})[{}[]]))({[<><>]}<<<>{}
+[{[[[{<<(({[({[][]}<[]<>>)<{{}()}{{}}>]{({[]}[<>{}]){<[][]>[{}{}]}}})[[([<<>()>(<>[])]<<<>
+<({<<[(({[([{[()[]]({}{})}{{()[]}[()[]]}])[([((){}){<><>}]{<()[]>{{}{}}})]][[{<[()()]({}<>
+[{<([<({{<<[((<>[])(<><>))((()[])([][]))][(([][])<<>()>)]>[<<{()<>}<{}<>>><<{}<>>{()<>}]><{[()[
+[<{[<([{((({<<[]{}><{}{}>>([{}<>]<<><>>)})[[(<{}<>>([]<>))<<{}()>{{}<>}>]{[<[]<>>][[{}<>]<{}[
+({<{<[<({([<{<()()>{{}[]}}({<>{}})><{[[]<>]<[]()>}<[{}()]{{}[]}>>])}([<<[{[]<>}<<><>>][<[]{
+{[({<[[<<<(<{<{}<>>(()())}[{()}{()<>}]>)[<{{(){}}(()<>)}>{[([]{})(()<>)]{[(){}]{()[]}}}]>{{[<<[]()><()<>>>{
+<[{{({({(<<{[(()<>){[]()}][<[]>(()())]}{<(<><>}{()[]}>}>(<<{{}()}<[][]>>[{()<>}{{}{}}]>)>)}<[(<((<(
+[<{[<[{[[[([<(<>{}){{}<>}>(<<>{}>{{}{}})]{({<>[]}<{}()>)<({}<>)<{}{}>>}){<[[[]{}]{{}{}}]<<[]<>>(()[])>
+{[{((<(<[(((<({}[]){[]()}>)))]([{<(<<>{}>[[]])<[[][]][(){}]>>[{[{}<>]{[]<>}}{(<>())(())}]}[{<{{}()}<<>[]>>}[[
+[[[{{(<<<<((<((){}){[]<>}><<(){}><()<>>>){[<[][]>({}[])](({}{})<[][]>)})[[{(<>>}([{}()][{}()])]]>>>((<{[
+[[({<[[<([<[((<>{})({}<>))({{}{}}(()[]))]<<((){})<()()>>[<[][]><{}{}>]>>({[<()()>[[][]]]})])>
+([<(<{(<<[<{{([]<>)[<>[]]}<<()()>[(){}]>}><([[<>[]]](({}[])))({(()())<(){}>}<[<>>[()()]>)>]>>)
+{(({([{[{(<[[((){})(<>{})]<(()())(()[]>>]{([{}]{[][]})}>)<((((()<>)[<><>])<((){})[()()]>)[[<()<>>][<{}
+{{([{{<<({{<<<[]()><()[]>}{{()<>}}>[<{()<>}<[]{}>><{{}[]}[{}[]]>]}})({{({[<>{}]<(){}>}(<<>>(()<>)))(<
+<[[{<(<{{<[<{({}())}({[][]}{<><>})>{[<<>{}><()[]>]<[<>[]]<<>[]]>}]>(({[{[]()}<[]<>>]{<<>><<>[]>}}))}([[<
+([{<[{<({{[((<{}<>>[(){}])({()<>})){{<<>{}>}[<{}()>{()[]}]}]}[{(({()[]}(<><>))[<{}()>(<>[])])<[{()[]}[
+{<[{({<((<({[{[][]}{{}[]}]{[<>()][<>{}]}}((({}())([]()))<([][])[[][]]>)}({[[[][]]({}())]}{({{}}){(<>[])
+{{[{{({(<(<[[[[]{}](<><>)]([[]{}]{<>[]})]>({{{()[]}([])}[{[][]}(<><>)]](({[]}<<>[]>))))>)}({{[{{(([])
+[<[{[{<<({{[{[<>{}]<(){}>}]}<{(({}()){{}<>})(<{}()>{[]<>})}{<[[]{}]>}>}[<[[([][])[[]]]]{{([]())[{}<>]}<({
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+<[<{[[[<{{[[([[]<>]{(){}))[[{}<>][[][]]]](([<>[]]<<>[]>)[(()<>){()<>}])]}[<<((())(<>{}))<{[]()}<[
+[{[[{[[(<<(<({{}[])[<>()])><[[[]()](<>())]<{[]<>}({}())>>){[<{<>{}}[[]<>]>]}>{{<[<<>()>[()[]]
+[(([{(([{<[<[<{}[]>[<><>]]>({[{}{}]{[]{}}})]>}{{[[<[{}{})<()()>>{{<>}{{}[]}}]{{([][])[<>{}]}{
+(((<<<<[(<[<{{()()}<[]{}>}<{[][]}{<>[]}>>[[[()()]{{}{}}]]]({[<()()><[]{}>]{{[]{}}([]())}}<{<()<>>[<>]}<<{}
+<([<[[<<[(({(({}())<{}>)<(()[])[{}[]]>})<<({{}}[[]{}])[({}{})((){})]><<{{}()}{[][]}>>>)]>[[(
+<<<{(<{{(([{<{()[]}><<[]{}>{{}[]}>}{(<[][]>[[]<>])[{()<>}]}](<[[<><>][<>[]]]([()[]]<{}()>)>))<(
+{[[([<<[[(<((<()()>(<><>))[[{}()]<()<>>]){[((){}){[]{}}][[{}[]]]}>([<((){}){(){}}>[([]{}){()[]}]]))]<[<<{<<><
+([{[{([<{{{[<(()[])({}())>{[<>{}]{{}<>}}]{(([]<>){<>}){[()<>]<()[]>}}}(<<[{}<>](()[])>{[[]()]
+[<((<<<[{[((([<>{}]){[(){}]})<<{<>{}}({}[])>[[[]{}]<()[]>]>){<(<<>()>(<>[]))[(()[]){[]<>}]>
+<(([({[[[[<<[[[]()]]<<()[]>>>>{{<[()[]]{{}{}}>{<[]()>{()[]}}}<[({}<>)[()<>]]>}]([([[()()]<<>{}>])<{<{
+<{([([((<{{[([()[]]{{}()})][(<<><>>){{{}[]}[[]<>]}]}}>[((<(<<>>[[]<>])[(()[]){()<>]]><<{{}
+{<[[({{<<[<<<{()[]}<<>{}>>([[]<>]((){}))>[{[<>()]{{}<>}}[({}())]]>{[{{[]()}({}())>]({{(){}}<()<>>}{<(){}>{
+{(<[{[{{[<(<({(){}}<[]()>)(<<>[]>{<>{}})>)>]({[{[({}()){<><>}]<[[]<>]{<>{}}>}(<<{}{}>([]<>)>(({}{}){(
+((<((((<<({[{{{}[]}(()())}{<()()>}]<[[<>[]][(){}]][{()[]}]>}(([<[][]>][<[]()>({}[])])[<<[]()>[{}<>
+[[{<[(<{{<{<[{<>()}[[]]]({{}<>})>{{{()[]}<{}<>>}}}<({{()[]}}[[<>()](()[])])<[([]<>)[{}<>]][([][]
+<{{[{[{(<<({{{{}[]}{[]<>}}<[[]{}]{{}[]}>}[({{}{}}<[]()>){[[]<>]}])((<{()()}[[]{}]>({()<>}<
+({{{<({{<<[<[{()<>}[[]<>]]<[{}{}][<>[]]>>({[{}()]<<>>}[(<><>)({}())])][([{<>()}{<>{}}]{(<>()){()[]
+[((<({(<<({[<(<>{})<[]<>>>[([])[(){}]]][{{()<>}(<><>)]<[{}{}][{}<>]>]}{<{(<><>)[{}[]]}(([])[[]{
+(([{<[<{<<{{({()[]}{<>{}})[[[]<>]<[][]>]}<{<()<>>[()()]}{<<>><()<>>}>}>>[<[[<[{}<>]{[]{}}><(<
+(<<<[<<<(([{{<()<>>[<>[]]}{<()[]>([][])}}])(([{{{}{}}[<>()]}({<>()}{[]{}})]<[<<>[]>]{({}<>){[]<>}
+{<<[<([[({({{<{}[]>([]{})}[<()<>>[(){}]]}{[(()<>)]{<()[]>({}[])}}){<([{}[]]({}<>))(({}{})(()<>))><([(){}]<{}
+{{[[<(<({<([[{[]{}}(()[])]<(<>[])>])({[[{}[]]({}<>)]})>[(<<[{}{}]<[]<>>>>{{{[]<>}[{}()]}({<><>}<<>()])}){([<
+{[[{{<(({(([[<()>{()<>}]([[]()]([][]))]<<({}[]){[][]}>([<><>]{()()})>)((<[<><>]{[]<>}>[[[][])[[]<>]
+[[<<{[[{([<{({[]()}({}())){{{}<>}<()()>}}([{{}()}<{}()>][{<>}[()<>]])><{{{{}[]}(<><>)}{[[]<>]<[]<>>}}>])}
+({(({(<({[{((<{}><{}>){<{}()>[{}[]]})}]{[<({<><>}({}()))>{{({}<>)(()<>)}{<{}{}>{<>[]}}}]}}({[{([[]{}])[<()
+({[{<<[<<[{{{{[][]}[()[]]}<<{}()>{{}()}>}{({<><>}([]))[<{}<>>(<>{})]}}{[([<>{}][()<>])([()[]])]}]<{[(<<><>
+{<{<(({[[{(({{()<>}[[]<>]}[[()<>][()()]])(<((){})[<><>]>{[[]<>][()<>}}))}<[<{{{}}[{}[]]}<(
+{{<[[(<[{<<((<{}<>>{(){}}))((<[]<>><{}{}>)({<>()}<()<>>))>>({[{(()[])<{}<>}}(<()()>)][<[<>{}]{<>
+<[<{((([<(<<((<>())<<>()>)>(<{<>()}{[]<>]>)>)[[{{{()[]}(()())}{({}())({}<>)}}](<[{()()}<()()>]((()){<>[]})><[
+(<([{[[[[[(<(<<>{}>)<{{}{}}>>(<<[]()><[]()>>(<(){}]{()()})))]]]({(<{(<()>([]{}))[{()<>}{[][]}]}([<
+(([({{{<(<{[<[<>[]](<>())>(<{}{}>)]<(([]<>>(()[]))(<()()>(<>{}))>}>({{[{[][]}][{[]<>}([]{})]}(<(()
+({({<{[{{([(<(()())><{[]{}}(<>())>)(<[()()]{()()}>[[[]()](<><>)])]{<<[[]<>](<>())>(({}{})<<><>>)>
+((([[{[<[{(<[{<><>}{{}<>})>{<[<>{}](<>)>[<[][]><[]{}>]}){[{{()[]}<<><>>}<(<><>)({}{})>]{<{(
+[[<({([{{[<{<(()())<[]<>>>{[[]{}]}}(<[{}<>]<<>()>><(()<>)[()()]>)>>{<{<[[]<>]{[]()}>{<[]<>>{[
+(({[[(([[<{([[{}<>]{()()}][[{}[]]{[]{}}]){[[()[]]<[][]>][<{}{}><{}{}>]}}[{[({}())[[]<>]]}{[({})<<>>]<{<>[]}
diff --git a/10/sample.txt b/10/sample.txt
new file mode 100644
index 0000000..2f182d8
--- /dev/null
+++ b/10/sample.txt
@@ -0,0 +1,10 @@
+[({(<(())[]>[[{[]{<()<>>
+[(()[<>])]({[<{<<[]>>(
+{([(<{}[<>[]}>{[]{[(<()>
+(((({<>}<{<{<>}{[]{[]{}
+[[<[([]))<([[{}[[()]]]
+[{[{({}]{}}([{[{{{}}([]
+{<[[]]>}<{[{[{[]{()[[[]
+[<(<(<(<{}))><([]([]()
+<{([([[(<>()){}]>(<<{{
+<{([{{}}[<[[[<>{}]]]>[]]
\ No newline at end of file