import java.util.*;

public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		int n = sc.nextInt();
		int k = sc.nextInt();
		String s = sc.next();
		
		//解説にあったimos法を使ってみる
		//配列に深さを代入
		int[] ar = new int[n];
		int depth = 1;
		int c1 = 1;
		ar[0] = depth;
		for (int i=1; i<n; i++) {
			String s1 = s.substring(i-1,i);
			String s2 = s.substring(i,i+1);
			if (s1.equals("(") && s2.equals("(")) {
				depth++;
				ar[i] = depth;
			}
			else if (s1.equals(")") && s2.equals(")")) {
				depth--;
				ar[i] = depth;
			}
			else {
				ar[i] = depth;
			}
			if (i+1 == k) {c1 = depth;}
		}
		
		if (s.substring(k-1,k).equals("(")) {
			for (int i=k; i<s.length(); i++) {
				if (ar[i]==c1) {System.out.println(i+1); break;}
			}
		}
		else {
			for (int i=k-2; i>=0; i--) {
				if (ar[i]==c1) {System.out.println(i+1); break;}
			}
		}
	} 
}