#include <iostream>
#include <string>
using namespace std;

int main()
{
    int n,k;
    cin >> n >> k;

    string s;
    cin >> s;

    int l = 0,r = 0;
    if(s[k-1] == '('){
        for(int i = k-1; i < n; i++){
            if(s[i] == '('){
                l++;
            }else{
                r++;
                if(l == r){
                    cout << i+1 << endl;
                    return 0;
                }
            }
        }
    }else{
        for(int i = k-1; i >= 0; i--){
            if(s[i] == ')'){
                r++;
            }else{
                l++;
                if(r == l){
                    cout << i+1 << endl;
                    return 0;
                }
            }
        }
    }
}