字符串括号匹配

#include <bits/stdc++.h>
using namespace std;
int main(void) {
    string s;
    cin >> s;
    int depth = 0;
    bool flag = true;
    for (const auto &c: s) {
        if (c == '(') {
            ++depth;
        } else if (c == ')') {
            --depth;
            if (depth < 0) {
                flag = false;
                break;
            }
        } else if (c == '@') {
            break;
        }
    }
    if (depth > 0) flag = false;
    cout << (flag ? "YES" : "NO") << endl;
    return 0;
}