import java.util.Scanner;

public class pre {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
		
		int n,k;
		n = sc.nextInt();
		k = sc.nextInt();
		
        String s = sc.next();
		
		int count = 0;
		int i;
		
		if(s.charAt(k-1) == '('){
			for(i=k-1;i<n;i++){
				if(s.charAt(i) == '(')
					count++;
				else
					count--;
					
				if(count == 0){
					System.out.println(i+1);
					break;
				}
			}
			
		}
		else{
			for(i=k-1;i>=0;i--){
				if(s.charAt(i) == ')')
					count++;
				else
					count--;
					
				if(count == 0){
					System.out.println(i+1);
					break;
				}
			}
		}

    }
}