diff --git a/src/bin/day13.rs b/src/bin/day13.rs
index 4a83ce7..7fdbd81 100644
--- a/src/bin/day13.rs
+++ b/src/bin/day13.rs
@@ -24,8 +24,8 @@ impl Pattern {
             .find(|&x| {
                 let d = min(x + 1, self.map[0].len() - x - 1);
 
-                iproduct!(0..self.map.len(), (0..d))
-                    .filter(|&(y, dx)| self.map[y][x - dx] != self.map[y][x + dx + 1])
+                iproduct!(0..self.map.len(), (1..=d))
+                    .filter(|&(y, dx)| self.map[y][x + 1 - dx] != self.map[y][x + dx])
                     .count()
                     == allowed_error
             })
@@ -37,8 +37,8 @@ impl Pattern {
             .find(|&y| {
                 let d = min(y + 1, self.map.len() - y - 1);
 
-                iproduct!(0..self.map[y].len(), (0..d))
-                    .filter(|&(x, dy)| self.map[y - dy][x] != self.map[y + dy + 1][x])
+                iproduct!(0..self.map[y].len(), (1..=d))
+                    .filter(|&(x, dy)| self.map[y + 1 - dy][x] != self.map[y + dy][x])
                     .count()
                     == allowed_error
             })