#include <bits/stdc++.h>

int main() {

  std::string str;
  int count = 1;
  int N, K;

  std::cin >> N >> K;
  std::cin >> str;

  if( str[K-1] == '(' ) {
    for(int i = K; K < N; ++i) {
      if( str[i] == '(' ) ++count;
      else                --count;

      if( count == 0 ) {
	std::cout << i+1 << std::endl;
	return 0;
      }
    }
  }
  else {
    for(int i = K-2; K >= 0; --i) {
      if( str[i] == ')' ) ++count;
      else                --count;

      if( count == 0 ) {
	std::cout << i+1 << std::endl;
	return 0;
      }
    }
  }   
    
  return 0;
}