#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ul;
typedef signed long long ll;
ul over = 1000000007;

int main(void)
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed;
  ll n, k;
  string s;
  cin >> n >> k >> s;
  k--;
  ll depth[n];
  depth[0] = 1;
  for (int i = 1; i < n; ++i) {
    if (s[i] != s[i-1]) depth[i] = depth[i-1];
    else if (s[i] == '(') depth[i] = depth[i-1]+1;
    else depth[i] = depth[i-1]-1;
  }
  if (s[k]=='(') {
    for (ll i = k+1; i < n; ++i) {
      if (depth[i]==depth[k]) {cout << i+1 << endl; return 0;}
    }
  } else {
    for (ll i = k-1; i >= 0; --i) {
      if (depth[i]==depth[k]) {cout << i+1 << endl; return 0;}
    }
  }
  return 0;
}