import java.util.*;
import java.io.*;
class Aaf {
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int K = scan.nextInt()-1;
    int ans = 0 , j = 0;
    char [] S = scan.next().toCharArray();
    for(int i=0; i<=N; i++){
      if(S[K]=='('){
        if(S[K+i]=='('){
          j=j+1;
          }else{
          j=j-1;
        }
      }else{
        if(S[K-i]=='('){
          j=j+1;
          }else{
          j=j-1;
        }
      }
      if(j==0){
        ans=i;
        break;
      }
    }
    if(S[K]=='('){
      ans=K+ans+1;
      }else{
      ans=K-ans+1;
    }
    System.out.println(ans);
  }
}