import java.util.*;
public class Main {
    public static void main(String[] args) throws Exception {
        Scanner koko = new Scanner(System.in);
        int n = koko.nextInt();
        int x = koko.nextInt();
        String a = koko.next();
        char[] aa = a.toCharArray();
        int count = 0;
        if(aa[x-1]=='('){
            for(int i=0; i<n-x+1; i++){
                if(aa[x-1+i]=='('){
                    count = count + 1;
                }else{
                    count = count - 1;
                    if(count==0){
                        System.out.println(x+i);
                        break;
                    }
                }
            }
        }else{
            for(int i=x-1; i>=0; i--){
                if(aa[i]==')'){
                    count = count + 1;
                }else{
                    count = count - 1;
                    if(count==0){
                        System.out.println(i+1);
                        break;
                    }
                }
            }
        }
    }
}