import java.util.Scanner;
class Kakko{
	public static void main(String args[]){
		Scanner s = new Scanner(System.in);
		int n = s.nextInt();
		int k = s.nextInt();
		String str = s.next();
		int count = 0;
		
		if(str.charAt(k - 1) == '('){
			for(int i = k; i < n; i++){
				char a = str.charAt(i);
				if(a == '('){
					count++;
				}else{
					count--;
				}
				if(count == -1){
					System.out.println(i + 1);
					System.exit(0);
				}
			}
		}else{
			for(int i = k - 2; i >= 0; i--){
				char a = str.charAt(i);
				if(a == ')'){
					count++;
				}else{
					count--;
				}        
				if(count == -1){
					System.out.println(i + 1);
					System.exit(0);
				}
			}
		}
	}
}