/* test3：多函数协作（函数调用 + 全局变量）*/
int a;
int b;

int sum() {
    return a + b;
}

int product() {
    return a * b;
}

int main() {
    int s;
    int p;
    a = 3;
    b = 4;
    s = sum();
    p = product();
    return s + p;
}