diff --git a/Aoc2024/Day01/Parser.lean b/Aoc2024/Day01/Parser.lean
index af16704..3076fae 100644
--- a/Aoc2024/Day01/Parser.lean
+++ b/Aoc2024/Day01/Parser.lean
@@ -3,29 +3,12 @@ import Std
 open Std.Internal.Parsec.String
 open Std.Internal.Parsec
 
-def splitOnWhitespace (s : String) : List String :=
-  s.split Char.isWhitespace |> .filter (· ≠ "")
-
-def parseNumber (s: String) : Except String Int :=
-  s.toInt? |> getOrThrow s!"Failed to parse as number: {s}"
-
-def getTwoElements (l : List α) : Except String (α × α) := do
-  let [a, b] := l | throw s!"Expected two elements, but got {l.length}"
-  pure (a, b)
-
-def parseTwoNumbers (line : String) : Except String (Int × Int) := do
-  let (a, b) ← getTwoElements (splitOnWhitespace line)
-  Prod.mk <$> parseNumber a <*> parseNumber b
-
-def parseLines (s : String) : Except String (List (Int × Int)) :=
-  s.splitOn "\n" |>.mapM parseTwoNumbers
-
-def lineParser : Parser (Int × Int) := do
+private def lineParser : Parser (Int × Int) := do
   let a ← String.digits
   let _ <- String.ws
   let b ← String.digits
   pure (a, b)
 
--- def inputParser : Parser (List (Int × Int)) := do
---   let lines ← lineParser.many1
---   pure lines
+private def inputParser : Parser (List (Int × Int)) := sepBy lineParser (String.skipChar '\n')
+
+def parseLines : String -> Except String (List (Int × Int)) := inputParser.run
diff --git a/Aoc2024/Day01/Solve.lean b/Aoc2024/Day01/Solve.lean
index f25a711..a82920b 100644
--- a/Aoc2024/Day01/Solve.lean
+++ b/Aoc2024/Day01/Solve.lean
@@ -2,7 +2,7 @@ import Aoc2024.Day01.Parser
 import Aoc2024.Utils
 namespace Aoc2024.Day01
 
-def exampleInput :=
+private def exampleInput :=
 "3   4
 4   3
 2   5
@@ -10,7 +10,7 @@ def exampleInput :=
 3   9
 3   3"
 
-def solvePart1 (pairs : List (Int × Int)) : Int :=
+private def solvePart1 (pairs : List (Int × Int)) : Int :=
   let (firsts, seconds) := pairs.unzip
   let distance (a b : Int) : Int := (a - b).natAbs
   (firsts.mergeSort.zipWith distance seconds.mergeSort) |> sumList
@@ -19,7 +19,7 @@ def parseAndSolvePart1 : String -> Except String Int := .map solvePart1 ∘ pars
 
 #guard (parseAndSolvePart1 exampleInput == Except.ok 11)
 
-def solvePart2 (pairs : List (Int × Int)) : Int :=
+private def solvePart2 (pairs : List (Int × Int)) : Int :=
   let (firsts, seconds) := pairs.unzip
   let similarityScore (n : Int) : Int := seconds.count n * n
   firsts |> sumListBy similarityScore
diff --git a/Aoc2024/Utils.lean b/Aoc2024/Utils.lean
index 215d194..0f39d1b 100644
--- a/Aoc2024/Utils.lean
+++ b/Aoc2024/Utils.lean
@@ -1,3 +1,7 @@
+import Std
+open Std.Internal.Parsec.String
+open Std.Internal.Parsec
+
 def sumList (nums : List Int) : Int := nums.foldl (· + ·) 0
 
 #guard sumList [] = 0
@@ -38,3 +42,14 @@ def getOrThrow (message : String) : Option α -> Except String α
 
 #guard (getOrThrow "Error" (some 42) == Except.ok 42)
 #guard (getOrThrow "Error" (none : Option Int) == Except.error "Error")
+
+def sepBy (p : Parser α) (sep : Parser β) : Parser (List α) :=
+  (do
+    let x ← p
+    let xs ← many (sep *> p)
+    pure (x :: xs.toList)
+  ) <|> pure []
+
+#guard (sepBy digits (skipChar ',')).run "1,2,3" == .ok [1, 2, 3]
+#guard (sepBy digits (skipChar ',')).run "4" == .ok [4]
+#guard (sepBy digits (skipChar ',')).run "" == .ok []