using System;
using System.Collections.Generic;

namespace No22_ParenthesesCorrespondence
{
    internal class Program
    {
        static void Main(string[] args) {
            string[] param = Console.ReadLine().Split(' ');
            int n = int.Parse(param[0]);
            int k = int.Parse(param[1]);
            string s = Console.ReadLine();

            bool leftFlag = false;
            bool rightFlag = false;
            int count = 0;
            Stack<(char C, int I)> stack = new Stack<(char, int)> ();
            for(int i = 0; i < n; i++) {
                stack.Push((s[i], i));
                if (i == k - 1) {
                    if (s[i] == '(') {
                        leftFlag = true;
                    } else {
                        rightFlag = true;
                    }
                }
                if (s[i] == '(') {
                    count++;
                } else {
                    if (0 < count) {
                        while (stack.Pop().C != '(') { }
                        count--;
                    }
                }
                if (leftFlag) {
                    if (stack.Count < k) {
                        Console.WriteLine(i + 1);
                        return;
                    }
                }
                if(rightFlag) {
                    Console.WriteLine(stack.Count + 1);
                    return;
                }
            }
        }
    }
}