/* -*- coding: utf-8 -*-
 *
 * 22.cc: No.22 括弧の対応 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

typedef stack<int> si;

/* global variables */

/* subroutines */

/* main */

int main() {
  int n, k;
  string s;
  cin >> n >> k >> s;
  k--;

  si st;
  for (int i = 0; i < n; i++) {
    if (s[i] == '(') st.push(i);
    else {
      int j = st.top(); st.pop();
      int ans = -1;
      if (j == k) ans = i;
      else if (i == k) ans = j;
      if (ans >= 0) {
	printf("%d\n", ans + 1);
	break;
      }
    }
  }
  return 0;
}