#include <bits/stdc++.h>
using namespace std;

signed main(){
  int N, K; cin >> N >> K;
  string S; cin >> S;
  stack< int > pos;
  for( int i = 0; i < N; ++i ){
    if( S[ i ] == '(' )
      pos.emplace( i );
    else{
      if( i + 1 == K )
        cout << pos.top() + 1 << endl,
        exit( 0 );
      else if( pos.top() + 1 == K )
        cout << i + 1 << endl,
        exit( 0 );
      else
        pos.pop();
    }
  }
  return 0;
}