using System;

namespace No022_括弧の対応
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] input = Console.ReadLine().Split(' ');
            int n = int.Parse(input[0]);
            int k = int.Parse(input[1]);
            string s = Console.ReadLine();
            int count, level = 2;

            if (n / 2 > k)
            {
                count = k;
                do
                {
                    if (s[count] == '(')
                        level++;
                    else
                        level--;

                    count++;
                } while (level != 1);
            }
            else
            {
                count = k - 2;
                do
                {
                    if (s[count] == ')')
                        level++;
                    else
                        level--;

                    count--;
                } while (level != 1);
                count += 2;
            }

            Console.WriteLine(count.ToString());
        }
    }
}