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

int main() {
    int n,k;
    string s;
    cin >> n >> k >> s;
    int ans = 0;
    if(s[k-1] == '('){
        for(int i = k-1;i < n;i++){
            if(s[i] == '(')ans++;
            else ans--;
            
            if(ans == 0){
                ans = i+1;
                break;
            }
        }
    }
    else{
        for(int i = k-1;i >= 0;i--){
            if(s[i] == '(')ans++;
            else ans--;
            
            if(ans == 0){
                ans = i+1;
                break;
            }
        }
    }
    
    cout << ans << endl;
    return 0;
}