diff --git a/src/exercises/day_9.ts b/src/exercises/day_9.ts
index 820e512..18c69b4 100644
--- a/src/exercises/day_9.ts
+++ b/src/exercises/day_9.ts
@@ -96,39 +96,92 @@ function is_area_red_green(
   //  - Every surround must form a line
   // old: Every corner needs to be surrounded
   // Error 1: 4560365591
+  // Error 2: 248032161
+  // Error 3: 4638219675
+  // NOTE: I do not need to verify every wall, just the opposite corners
   // Verify left wall
-  // floor.red_tiles.some((tile) => {
-  //   // point and side or point and point and the inverse
-  // });
-  const l_cover =
-    floor.red_tiles.some((tile) =>
-      tile.x <= tl_corner.x && tile.y <= tl_corner.y
-    ) && floor.red_tiles.some((tile) =>
-      tile.x <= bl_corner.x && tile.y >= bl_corner.y
-    );
-  // r
-  const r_cover =
-    floor.red_tiles.some((tile) =>
-      tile.x >= tr_corner.x && tile.y <= tr_corner.y
-    ) && floor.red_tiles.some((tile) =>
-      tile.x >= br_corner.x && tile.y >= br_corner.y
-    );
-  // b
-  const b_cover =
-    floor.red_tiles.some((tile) =>
-      tile.x <= bl_corner.x && tile.y >= bl_corner.y
-    ) && floor.red_tiles.some((tile) =>
-      tile.x >= br_corner.x && tile.y >= br_corner.y
-    );
-  // t
-  const t_cover =
-    floor.red_tiles.some((tile) =>
-      tile.x >= tr_corner.x && tile.y <= tr_corner.y
-    ) && floor.red_tiles.some((tile) =>
-      tile.x <= tl_corner.x && tile.y <= tl_corner.y
-    );
+  const ls_cover = floor.red_tiles.some((tile) => {
+    return (tile.x === tl_corner.x && tile.y <= tl_corner.y &&
+      ((floor.red_tiles.some((tile_2) =>
+        tile_2.x === tile.x && tile_2.y >= bl_corner.y
+      )) || (floor.red_tiles.some((tile_3) =>
+        tile_3.x <= tile.x && tile_3.y >= bl_corner.y &&
+        floor.red_tiles.some((tile_4) =>
+          tile_3.x <= tile_4.x && tile_3.y === tile_4.y
+        )
+      )))) ||
+      (tile.x === bl_corner.x && tile.y <= bl_corner.y &&
+        ((floor.red_tiles.some((tile_2) =>
+          tile_2.x === tile.x && tile_2.y <= tl_corner.y
+        )) || (floor.red_tiles.some((tile_3) =>
+          tile_3.x <= tile.x && tile_3.y <= tl_corner.y &&
+          floor.red_tiles.some((tile_4) =>
+            tile_3.x <= tile_4.x && tile_3.y === tile_4.y
+          )
+        )))); // NOTE: should also compare with opposite situation (first side and then point or 2 sides)
+  });
+  const rs_cover = floor.red_tiles.some((tile) => {
+    return (tile.x === tr_corner.x && tile.y <= tr_corner.y &&
+      ((floor.red_tiles.some((tile_2) =>
+        tile_2.x === tile.x && tile_2.y >= br_corner.y
+      )) || (floor.red_tiles.some((tile_3) =>
+        tile_3.x <= tile.x && tile_3.y >= br_corner.y &&
+        floor.red_tiles.some((tile_4) =>
+          tile_3.x <= tile_4.x && tile_3.y === tile_4.y
+        )
+      )))) ||
+      (tile.x === br_corner.x && tile.y >= br_corner.y &&
+        ((floor.red_tiles.some((tile_2) =>
+          tile_2.x === tile.x && tile_2.y <= tr_corner.y
+        )) || (floor.red_tiles.some((tile_3) =>
+          tile_3.x <= tile.x && tile_3.y <= tr_corner.y &&
+          floor.red_tiles.some((tile_4) =>
+            tile_3.x <= tile_4.x && tile_3.y === tile_4.y
+          )
+        )))); // NOTE: should also compare with opposite situation (first side and then point)
+  });
+  const ts_cover = floor.red_tiles.some((tile) => {
+    return (tile.x <= tl_corner.x && tile.y === tr_corner.y &&
+      ((floor.red_tiles.some((tile_2) =>
+        tile_2.x >= tr_corner.x && tile_2.y === tile.y
+      )) || (floor.red_tiles.some((tile_3) =>
+        tile_3.x >= tile.x && tile_3.y <= tr_corner.y &&
+        floor.red_tiles.some((tile_4) =>
+          tile_3.x === tile_4.x && tile_3.y >= tile_4.y
+        )
+      )))) ||
+      (tile.x >= bl_corner.x && tile.y === br_corner.y &&
+        ((floor.red_tiles.some((tile_2) =>
+          tile_2.x <= br_corner.x && tile_2.y === tile.y
+        )) || (floor.red_tiles.some((tile_3) =>
+          tile_3.x >= tile.x && tile_3.y >= br_corner.y &&
+          floor.red_tiles.some((tile_4) =>
+            tile_3.x === tile_4.x && tile_3.y >= tile_4.y
+          )
+        )))); // NOTE: should also compare with opposite situation (first side and then point)
+  });
+  const bs_cover = floor.red_tiles.some((tile) => {
+    return (tile.x <= bl_corner.x && tile.y === bl_corner.y &&
+      ((floor.red_tiles.some((tile_2) =>
+        tile_2.x >= tr_corner.x && tile_2.y === tile.y
+      )) || (floor.red_tiles.some((tile_3) =>
+        tile_3.x >= tile.x && tile_3.y >= br_corner.y &&
+        floor.red_tiles.some((tile_4) =>
+          tile_3.x === tile_4.x && tile_3.y <= tile_4.y
+        )
+      )))) ||
+      (tile.x >= tr_corner.x && tile.y === tr_corner.y &&
+        ((floor.red_tiles.some((tile_2) =>
+          tile_2.x <= tl_corner.x && tile_2.y === tile.y
+        )) || (floor.red_tiles.some((tile_3) =>
+          tile_3.x >= tile.x && tile_3.y <= tr_corner.y &&
+          floor.red_tiles.some((tile_4) =>
+            tile_3.x === tile_4.x && tile_3.y <= tile_4.y
+          )
+        )))); // NOTE: should also compare with opposite situation (first side and then point)
+  });
 
-  return l_cover && r_cover && b_cover && t_cover;
+  return ls_cover && rs_cover && ts_cover && bs_cover;
 }
 
 function calc_distance(a: Coordinate, b: Coordinate): number {