#include <iostream>
#include <string>
using namespace std;
int main(){
    int N, K; cin >> N >> K;
    string s; cin >> s;
    bool f_rev = false;
    if(s[K-1] == ')'){
        f_rev = true;
        string t = s;
        for(int i = 0; i < t.size(); i++){
            s[N-i-1] = (t[i]=='('?')':'(');
        }
        K = N - K + 1;
    }
    int res = -1, c = 1;
    for(int i = K; i < N; i++){
        if(s[i] == '(') c++;
        if(s[i] == ')') c--;
        if(c == 0){ res = i+1; break; }
    }
    cout << (f_rev?N-res+1:res) << endl;
}