import java.util.*;

public class Yukicoder_22{
	public static void main(String[] args){
		Scanner stdIn = new Scanner(System.in);
		int N = stdIn.nextInt();
		int K = stdIn.nextInt();
		String str = stdIn.next();

		char par = str.charAt(K-1);

		if(par == (char)'('){
			int count = 1;
			for(int i=K;i<N;i++){
				if(str.charAt(i) == (char)'('){
					count++;
				}
				else{
					count--;
				}

				if(count == 0){
					System.out.println(i+1);
					break;
				}
			}
		}
		else{
			int count = 1;
			for(int i=K-2;i>=0;i--){
				if(str.charAt(i) == (char)'('){
					count--;
				}
				else{
					count++;
				}

				if(count == 0){
					System.out.println(i+1);
					break;
				}
			}

		}



	}
}