diff --git a/du3/program.c b/du3/program.c
index e931095..e99e81f 100644
--- a/du3/program.c
+++ b/du3/program.c
@@ -89,7 +89,7 @@ int main()
         char input[1000];
         while (fgets(input,sizeof(input),stdin)!=NULL)
         {
-		if((input[0]>'A' && input[0]<'Z') || (input[0]>'a' && input[0]<'z'))
+		if((input[0]>='A' && input[0]<='Z') || (input[0]>='a' && input[0]<='z'))
 		{
 			printf("bad input\n");
 			return 0;