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();
        String [] arr = S.split("");
        int a=0;
        if( arr[K-1].equals(")") ){
            while(a!=-1){
                K--;
                if( arr[K-1].equals(")") ){
                    a++;
                }else{
                    a--;
                }
            }
        }else{
            while(a!=-1){
                K++;
                if( arr[K-1].equals("(") ){
                    a++;
                }else{
                    a--;
                }
            }
        }
        System.out.println(K);
    }
}