#include <bits/stdc++.h>
#define rep(i, n) for(long long i = 0; i < n; i++)
#define ALL(v) (v).begin(), (v).end()
using namespace std;

using lint = long long;

int main() {
    int n, k;
    string s;
    cin >> n >> k >> s;
    k--;
    stack<int> st;
    rep(i, n) {
        if (s[i] == '(') {
            st.emplace(i);
        } else {
            int tp = st.top();
            st.pop();
            if (tp == k || i == k) {
                cout << (tp == k ? i + 1 : tp + 1) << endl;
                return 0;
            }
        }
    }
}