diff --git a/labs/datalab/bits.c b/labs/datalab/bits.c
index 46d1fbe..993be6c 100644
--- a/labs/datalab/bits.c
+++ b/labs/datalab/bits.c
@@ -202,7 +202,7 @@ int negate(int x) {
  */
 int isAsciiDigit(int x) {
   x ^= 0x30;
-  return (!(x >> 4)) & ((~x >> 3) | ((~x >> 2) & (~x >> 1)));
+  return !((x | (x + 6)) >> 4);
 }
 /* 
  * conditional - same as x ? y : z