diff --git a/src/main.rs b/src/main.rs
index 7b8384d..0546b2c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -14,16 +14,16 @@ fn parse(input: &[u8]) -> &[u8] {
 fn main() {
     for input in INPUTS.iter() {
         let output = parse(input);
-        let score = solution(output);
+        let score = solution::<14>(output);
 
         println!("{}", score);
     }
 }
 
-fn solution(input: &[u8]) -> usize {
+fn solution<const N: usize>(input: &[u8]) -> usize {
     let mut buffer = [0; 26];
 
-    for &c in input.iter().take(4) {
+    for &c in input.iter().take(N) {
         buffer[(c - b'a') as usize] += 1;
     }
 
@@ -31,10 +31,10 @@ fn solution(input: &[u8]) -> usize {
         return 0;
     }
 
-    for i in 4..input.len() {
+    for i in N..input.len() {
         let c = input[i];
         buffer[(c - b'a') as usize] += 1;
-        let last = input[i - 4];
+        let last = input[i - N];
         buffer[(last - b'a') as usize] -= 1;
 
         if buffer.iter().all(|&c| c == 0 || c == 1) {
@@ -49,15 +49,27 @@ fn solution(input: &[u8]) -> usize {
 fn solution_bench(b: &mut test::Bencher) {
     b.iter(|| {
         let input = parse(INPUTS[1]);
-        let result = solution(input);
+        let result = solution::<14>(input);
         test::black_box(result);
     })
 }
 
 #[test]
 fn tests() {
-    assert_eq!(solution("bvwbjplbgvbhsrlpgdmjqwftvncz".as_bytes()), 5);
-    assert_eq!(solution("nppdvjthqldpwncqszvftbrmjlhg".as_bytes()), 6);
-    assert_eq!(solution("nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg".as_bytes()), 10);
-    assert_eq!(solution("zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw".as_bytes()), 11);
+    assert_eq!(
+        solution::<14>("bvwbjplbgvbhsrlpgdmjqwftvncz".as_bytes()),
+        23
+    );
+    assert_eq!(
+        solution::<14>("nppdvjthqldpwncqszvftbrmjlhg".as_bytes()),
+        23
+    );
+    assert_eq!(
+        solution::<14>("nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg".as_bytes()),
+        29
+    );
+    assert_eq!(
+        solution::<14>("zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw".as_bytes()),
+        26
+    );
 }