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

int main(int argc, const char * argv[]) {
    int n;
    cin >> n;
    int k;
    cin >> k;
    string s;
    cin >> s;
    string startString;
    string tmpString;
    int result;
    int count = 0;
    startString = s[k-1];
    if(startString == "("){
        for (int i = k; i < n; i++) {
            tmpString = s[i];
            if(tmpString == "("){
                count++;
            }
            else{
                if(count == 0){
                    result = i;
                    break;
                }
                else{
                    count--;
                }
            }
        }
    }
    else{
        for(int i = k - 2;i >= 0;i--){
            tmpString = s[i];
            if(tmpString == ")"){
                count++;
            }
            else{
                if(count == 0){
                    result = i;
                    break;
                }
                else{
                    count--;
                }
            }

        }
    }
    cout << result+1;
    cout << "\n";
}