#include <bits/stdc++.h>

using namespace std;

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

  int sz = s.size();
  vector<int> id(n);
  stack<int> st;
  for (int i = 0; i < sz; i++) {
    if (s[i] == '(') {
      st.push(i);
    } else {
      int v = st.top();
      st.pop();
      id[i] = v; id[v] = i;
    }
  }
  cout << id[k - 1] + 1 << endl;

  return 0;
}