#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef pair<int,int> P;
 
const int INF = 1e9;
const int mod = 1e9+7;
const double EPS = 1e-10;
const double PI = acos(-1.0);

int main()
{
    int n,k;
    cin >> n >> k;
    string s;
    cin >> s;
    int l = 0,r = 0,flag = 0,ans = 0;

    if(s[k-1] == '('){
        for(int i = 0; i < s.size(); i++){
            if(flag || i == k-1){
                flag = 1;
                if(s[i] == '(') l++;
                else r++;
                if(l == r){
                    ans = i+1;
                    break;
                }
            }
        }
    }else{
        for(int i = s.size()-1; i >= 0; i--){
            if(flag || i == k-1){
                flag = 1;
                if(s[i] == '(') l++;
                else r++;
                if(l == r){
                    ans = i+1;
                    break;
                }
            }
        }
    }
    cout << ans << endl;
}