#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int n, k;
  cin >> n >> k;
  --k;
  string s;
  cin >> s;
  stack<int> st;
  rep(i, n) {
    if (s[i] == '(') {
      st.push(i);
    }
    else {
      int l = st.top();
      st.pop();
      if (l == k) {
        cout << i + 1 << endl;
        break;
      }
      else if (i == k) {
        cout << l + 1 << endl;
        break;
      }
    }
  }
  return 0;
}