#include<iostream>
#include<string>

using namespace std;

int main(void){
  int n;
  int k;
  string c;

  int i;
  int j;

  cin>>n>>k;
  cin>>c;

  j=1;
  k--;

  if(c[k]=='('){
    for(i=k+1;i<n;i++){
      j+=(c.at(i)==')')?-1:1;
      if(j==0)
      break;
    }
  }else{
    for(i=k-1;i>=0;i--){
      j+=(c.at(i)==')')?1:-1;
      if(j==0)
      break;
    }
  }

  cout<<i+1<<endl;

  return 0;
}