import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int K = sc.nextInt();
    String s = sc.next();
    int ans = 0;
    if(s.charAt(K - 1) == '(') {
      int p = 1;
      for(int i = K; i < N; i++) {
        if(s.charAt(i) == '(') {
          p++;
        } else {
          p--;
        }
        if(p == 0) {
          ans = i + 1;
          break;
        }
      }
    } else {
      int p = -1;
      for(int i = K - 2; i >= 0; i--) {
        if(s.charAt(i) == '(') {
          p++;
        } else {
          p--;
        }
        if(p == 0) {
          ans = i + 1;
          break;
        }
      }
    }
    System.out.println(ans);
  }
}