diff --git a/2021/four.nim b/2021/four.nim
index f617b8a..d588d96 100644
--- a/2021/four.nim
+++ b/2021/four.nim
@@ -1,11 +1,61 @@
-import std/[strutils, sequtils, options, math, parseutils]
+import std/[strutils, sequtils, options, math, parseutils, sets]
 import ./common
 
+type Board = object
+  entries: seq[string]
+  checked: seq[int]
+
+let winningSets = [
+  [0, 1, 2, 3, 4],
+  [5, 6, 7, 8, 9],
+  [10, 11, 12, 13, 14],
+  [15, 16, 17, 18, 19],
+  [20, 21, 22, 23, 24],
+  [0, 5, 10, 15, 20],
+  [1, 6, 11, 16, 21],
+  [2, 7, 12, 17, 22],
+  [3, 8, 13, 18, 23],
+  [4, 9, 14, 19, 24]
+].mapIt(it.toHashSet())
+
+proc isBoardWinning(b: ref Board): bool =
+  let s = b.checked.toHashSet()
+  for w in winningSets:
+    if w < s:
+      return true
+  return false
+
+
 proc squidBingo(inputLines: seq[string]): int =
   var input: seq[string] = inputLines
-  let calledNumbers: seq[string] = input[0].split(',')
-  input.delete(0..1)
+  let calledNumbers: seq[string] = input[0].split ','
+  input.delete 0..1
+
   echo calledNumbers
+
+  # construct boards
+  var boards: seq[Board]
+  var board: Board = Board(entries: @[], checked: @[])
+  for l in input:
+    echo l
+    if l.strip() == "":
+      boards.add board
+      echo board.entries
+      board = Board(entries: @[], checked: @[])
+      continue
+    board.entries.add [l[0..1], l[3..4], l[6..7], l[9..10], l[12..13]].mapIt(it.strip())
+    
+  for n in calledNumbers:
+    for b in boards:
+      for i, e in b.entries:
+        if n == e:
+          # TODO: why can't I add here but I can add on 46?!
+          b.checked.add i
+      if b.isBoardWinning():
+        # TODO: get unchecked entries
+        # TODO: multiple their sum with last .checked
+        return 9
+
   return 0
 
 let input = 4.loadInput()
@@ -13,25 +63,23 @@ time("squidBingo part 1"): echo input.squidBingo()
 
 when not defined(release):
   static:
-    let testInput = """
-    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
+    let testInput = """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
 
-    22 13 17 11  0
-     8  2 23  4 24
-    21  9 14 16  7
-     6 10  3 18  5
-     1 12 20 15 19
+22 13 17 11  0
+ 8  2 23  4 24
+21  9 14 16  7
+ 6 10  3 18  5
+ 1 12 20 15 19
 
-     3 15  0  2 22
-     9 18 13 17  5
-    19  8  7 25 23
-    20 11 10 24  4
-    14 21 16 12  6
+ 3 15  0  2 22
+ 9 18 13 17  5
+19  8  7 25 23
+20 11 10 24  4
+14 21 16 12  6
 
-    14 21 17 24  4
-    10 16 15  9 19
-    18  8 23 26 20
-    22 11 13  6  5
-     2  0 12  3  7
-    """.strip().split('\n')
+14 21 17 24  4
+10 16 15  9 19
+18  8 23 26 20
+22 11 13  6  5
+ 2  0 12  3  7""".split('\n')
     doAssert testInput.squidBingo() == 4512