Update a1/program.c

a1/program.c

@@ -38,7 +38,7 @@ int main() {
             }
         } else if (isClosing(current)) {
             if (top == -1) {
-                printf("Unexpected closing bracket %c in %d.\n", current, i);
+                printf("Unexpected closing bracket %c in %d\n", current, i);
                 return 0;
             }
             if (!isMatching(stack[top], current)) {