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

int main(){
    int N, K, i, cnt = 1, tmp;
    string str;
    vector <int> num;

    cin >> N >> K >> str;
    for(i = 0; i < N; i++){
        if(str[i] == '('){
            num.push_back(cnt);
        }else{
            tmp = *(num.end() - 1);
            num.erase(num.end() - 1);
            if(str[K - 1] == '('){
                if(tmp == K){
                    cout << i + 1 << endl;
                    break;
                }
            }else{
                if(i == K - 1){
                    cout << tmp << endl;
                    break;
                }
            }
        }
        cnt++;
    }
    return 0;
}