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();

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