krsu 3405 (not my code)

#include "bits/stdc++.h"
using namespace std;

#define ar array
typedef long long ll;

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    string s;
    cin >> s;
    int n = s.size();
    queue<int> p;
    for (int i = 0; i < n; i++) {
        if (s[i] == '(')
            p.push(i);
    }

    int sum = 0, res = 0;
    for (int i = 0; i < n; i++) {
        if (s[i] == '(')
            sum++, p.pop();
        if (s[i] == ')')
            sum--;
        if (sum < 0) {
            sum += 2;
            for (int j = p.front() - 1; j >= i; j--) {
                swap(s[j], s[j + 1]);
                res++;
            }
            p.pop();
        }
    }

    cout << res << "\n";
}

/*

*/