diff --git a/Sources/aoc2021/04.swift b/Sources/aoc2021/04.swift
index f38d17a..1bc9053 100644
--- a/Sources/aoc2021/04.swift
+++ b/Sources/aoc2021/04.swift
@@ -58,13 +58,16 @@ struct Day04 {
             .map { Int($0)! }
         _ = lines.removeFirst() //empty seperator line
         
-        let boards = lines
+        let boardsInitial = lines
             .split(separator: "")
             .map { boardLines in
                 Board(numbers: boardLines.map { $0.split(separator: " ").map { num in Int(num)! } })
             }
-        var boardsA = boards
-        runA(boards: &boardsA, inputNumbers: inputNumbers)
+        var boards = boardsInitial
+        runA(boards: &boards, inputNumbers: inputNumbers)
+        
+        boards = boardsInitial
+        runB(boards: &boards, inputNumbers: inputNumbers)
     }
     
     func runA(boards: inout [Board], inputNumbers: [Int]) {
@@ -81,7 +84,17 @@ struct Day04 {
         }
     }
     
-    func runB(_ commands: [String]) {
-        
+    func runB(boards: inout [Board], inputNumbers: [Int]) {
+        for inputNumber in inputNumbers {
+            //print("\nInput: \(inputNumber)")
+            for (idx, var board) in boards.enumerated() {
+                //print("Checking board: \(idx)")
+                if !board.hasWon && board.crossOf(num: inputNumber) && board.checkHasWon() {
+                    print(board.calculateScore() * inputNumber)
+                    return
+                }
+                boards[idx] = board
+            }
+        }
     }
 }