#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n, k, c = 0, ans;
    string s;
    cin >> n >> k >> s;
    k--;
    if (s[k] == '(') {
        for (int i = k; i < n; i++) {
            if (s[i] == '(') c++;
            if (s[i] == ')') c--;
            if (c == 0) ans = i+1;
        }
    }
    else {
        for (int i = k; i >= 0; i--) {
            if (s[i] == '(') c++;
            if (s[i] == ')') c--;
            if (c == 0) ans = i+1;
        }
    }
    cout << ans << endl;
    return 0;
}