#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

int main(){
  int N, K; cin >> N >> K;
  K--;
  string S; cin >> S;
  vector<int> A(N);
  A[0] = 1;
  for(int i = 1; i < N; i++){
    if(S[i-1] == S[i]){
      if(S[i] == '(') A[i] = A[i-1] + 1;
      else A[i] = A[i-1] - 1;
    }else{
      A[i] = A[i-1];
    }
  }
  if(S[K] == '('){
    for(int i = K+1; i < N; i++){
      if(A[K] == A[i]){
        cout << i+1 << endl;
        return 0;
      }
    }
  }else{
    for(int i = K-1; i >= 0; i--){
      if(A[K] == A[i]){
        cout << i+1 << endl;
        return 0;
      }
    }
  }
}