diff --git a/3.py b/3.py
index 10eb917..cf4dea7 100644
--- a/3.py
+++ b/3.py
@@ -1,6 +1,7 @@
+from __future__ import annotations
 import sys
 
-bitstrings = []
+bitstrings: list[str] = []
 
 for x in sys.stdin:
     bitstrings.append(x.rstrip())
diff --git a/4.py b/4.py
new file mode 100644
index 0000000..418d778
--- /dev/null
+++ b/4.py
@@ -0,0 +1,62 @@
+import numpy as np
+
+
+def has_bingo(board: np.ndarray) -> bool:
+    for row in board:
+        if np.all(row == -1):
+            return True
+
+    for col in board.T:
+        if np.all(col == -1):
+            return True
+
+    return False
+
+
+def part_one(boards, number):
+    for number in numbers:
+        boards[boards == number] = -1
+
+        for board in boards:
+            if has_bingo(board):
+                return board[board != -1].sum() * number
+
+
+def part_two(boards: np.ndarray, number):
+    for number in numbers:
+        boards[boards == number] = -1
+
+        done_boards = []
+
+        for b, board in enumerate(boards):
+            if has_bingo(board):
+                done_boards.append(b)
+
+        if len(boards) == 1 and len(done_boards) == 1:
+            board = boards[0]
+            return board[board != -1].sum() * number
+
+        boards = np.delete(boards, done_boards, 0)
+
+
+if __name__ == "__main__":
+    numbers = [int(x) for x in input().split(",")]
+
+    input()  # Skip blank line
+
+    boards = []
+
+    try:
+        while True:
+            current_board = []
+            while (line := input().strip()) != "":
+                current_board.append([int(x) for x in line.split()])
+            boards.append(current_board)
+    except EOFError:
+        boards.append(current_board)
+
+    boards = np.array(boards)
+
+    print("Winning board:", part_one(boards.copy(), numbers))
+
+    print("Losing board :", part_two(boards.copy(), numbers))
diff --git a/ex4.in b/ex4.in
new file mode 100644
index 0000000..669a51d
--- /dev/null
+++ b/ex4.in
@@ -0,0 +1,19 @@
+7,4,9,5,11,17,23,2,0,14,21,24,10,16,13,6,15,25,12,22,18,20,8,19,3,26,1
+
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+14 21 16 12  6
+
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+10 16 15  9 19
+18  8 23 26 20
+22 11 13  6  5
+ 2  0 12  3  7
diff --git a/input4.in b/input4.in
new file mode 100644
index 0000000..59ebdb2
--- /dev/null
+++ b/input4.in
@@ -0,0 +1,601 @@
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