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diff --git a/2024/lean/Solutions/Day01.lean b/2024/lean/Solutions/Day01.lean
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+++ b/2024/lean/Solutions/Day01.lean
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+-- Day 1: Historian Hysteria
+
+def solution (input : String) : String :=
+  let input := input.stripSuffix "\n"|>.splitOn "\n"
+  let l1 := input.map <| fun x => x.splitOn "   " |>.get! 0 |>.toInt!
+  let l2 := input.map <| fun x => x.splitOn "   " |>.get! 1 |>.toInt!
+  let p1 :=
+    List.foldl (· + ·) 0 <|
+      List.zipWith (fun a b => (a - b).natAbs) l1.mergeSort l2.mergeSort
+  let p2 :=
+    List.foldl (· + ·) 0 <|
+      List.map (fun a => a * List.count a l2) l1
+  s!"{p1}, {p2}"
+
+-- def main (args : List String) : IO Unit := do
+--   let input <- IO.FS.readFile s!"../input/{args.get! 0|>.toLower}.txt"
+--   IO.println <| solution input