fix the problem

hello.c

@@ -7,7 +7,7 @@ void main(int argc, char* argv[]) {
 		printf("Hello %s!\n", argv[1]);
 	else {
 		printf("Hello ");
-		printf(argv[1]);
+		printf("%s",argv[1]);
 		for (int i=2; i < argc; i++)
 			printf(", %s", argv[i]);
 		printf("!\n");