diff --git a/src/day9.rs b/src/day9.rs
index d31fd6f..6c513ff 100644
--- a/src/day9.rs
+++ b/src/day9.rs
@@ -17,7 +17,7 @@ unsafe fn inner1(s: &[u8]) -> usize {
     macro_rules! insert_file {
         ($len:expr, $id:expr) => {
             let len = $len;
-            checksum += (disk_pos * 2 + len - 1) * $id * len / 2;
+            checksum += (disk_pos * 2 + len - 1) * $id * len;
             disk_pos += len;
         };
     }
@@ -50,7 +50,7 @@ unsafe fn inner1(s: &[u8]) -> usize {
 
     insert_file!(rem_src, left);
 
-    checksum
+    checksum / 2
 }
 
 pub fn part1(s: &str) -> impl Display {