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

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