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[] coresspond = new int[N];
    int a = 0;
    int b = N - 1;
    while(a < b) {
      boolean flg = true;
      if(s.charAt(a + 1) == ')') {
        coresspond[a] = a + 1;
        coresspond[a + 1] = a;
        a += 2;
        flg = false;
      } 
      if(s.charAt(b - 1) == '(') {
        coresspond[b] = b - 1;
        coresspond[b - 1] = b;
        b -= 2;
        flg = false;
      }
      if(flg) {
        coresspond[a] = b;
        coresspond[b] = a;
        a++;
        b--;
      } 
    }
    System.out.println(coresspond[K - 1] + 1);
  }
}