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

int main() {
  int n, k;
  string s;
  cin >> n >> k >> s;
  int sum[n] = {};
  int cnt = 0;
  for (int i = 0; i < n; ++i) {
    if (s[i] == '(') cnt++;
    else cnt--;
    sum[i] = cnt;
  }
  int res;
  if (s[k -1] == '(') {
    for (int i = k; i < n; ++i) {
      if (cnt[k - 1] - 1 == cnt[i]) {
        res = i + 1;
        break;
      }
    }
  } else {
    for (int i = k - 2; i >= 0; --i) {
      if (cnt[k - 1] + 1 == cnt[i]) {
        res = i + 1;
      }
    } 
  }
  cout << res << endl;
  return 0;
}