#include <iostream>
#include <vector>
#include <utility>
#include <set>
#include <list>
#include <cassert>
#include <queue>
#include <cmath>
#include <algorithm>
#include <stack>
#include <string>

using namespace std;
using ll = long long int;
#define REP(i, n) for(int i = 0; i < (int)(n); i++)
#define YES(n) std::cout << ((n) ? "YES" : "NO"  ) << "\n";
#define Yes(n) std::cout << ((n) ? "Yes" : "No" ) << "\n";

#define ALL_INCLUDED_ENVIRONMENT

template <class T, class Alloc, template <class, class> class C> std::ostream& operator<<(std::ostream& o, const C<T, Alloc>& v) {
  o << "{";
  bool init = 1;
  for (auto e : v) {
    if (init) { init = 0; }
    else { o << ", "; }
    o << e;
  }
  o << "}";
  return o;
}

ll n, k, ans;
string s;
stack<ll> stk;

int main() {
  // cin.tie(0);
  // ios::sync_with_stdio(false);
  cin >> n >> k; cin.ignore();
  getline(cin, s);
  k--;

  if (s[k] == ')') {
    REP (i, n) {
      if (i == k) {
        ans = stk.top()+1;
        break;
      }
      if (s[i] == '(') {
        stk.push(i);
      } else {
        stk.pop();
      }
    }
  } else {
    REP (i, n) {
      if (s[i] == '(') {
        stk.push(i);
      } else {
        if (stk.top() == k) {
          ans = i+1;
          break;
        }
        stk.pop();
      }
    }
  }
  cout << ans << "\n";
  return 0;
}