#include <iostream>
using namespace std;

int main ()
{
  int N, K;
  string s;
  cin >> N >> K >> s;

  int n = K;

  if  (s[K] == '(') {
    int cnt = 1;
    for (int i = K+1; i <= N; i++) {
      if (s[i] == '(') cnt++;
      else cnt--;
      if (cnt == 0) {
        cout << i-K << endl;
        break;
      }
    }
  }
  else {
    int cnt = -1;
    for (int i = K+1; i >= 1; i--) {
      if (s[i] == ')') cnt--;
      else cnt++;
      if (cnt == 0) {
        cout << i-K << endl;
        break;
      }
    }
  }
  return 0;
}