import java.util.Scanner;

public class Main{

	static final Scanner	s	=new Scanner(System.in);

	public static void main(String args[]){
		input();
		solve();
	}


	static int n,k;
	static String in;
	private static void input(){
		n=s.nextInt();
		k=s.nextInt()-1;
		in=s.next();
	}

	private static void solve(){
		int depth=0,i=k;
		switch(in.charAt(k)){
		case '(':
			while(true) {
				i++;
				if(depth==0&&in.charAt(i)==')') {
					System.out.println(i+1);
					return;
				}
				depth+=in.charAt(i)=='('?1:-1;
			}
		case ')':
			while(true) {
				i--;
				if(depth==0&&in.charAt(i)=='(') {
					System.out.println(i+1);
					return;
				}
				depth+=in.charAt(i)==')'?1:-1;
			}
		}
	}
}