diff --git a/du3/program.c b/du3/program.c
index 6531677..5a6c755 100644
--- a/du3/program.c
+++ b/du3/program.c
@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <ctype.h>
 #include <stdlib.h>
+#include <string.h>
 
 int main() {
 	char input[11];