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 = 0;

            count = k - 1;

            if (s[count] == '(')
            {
                do
                {
                    count++;

                    if (s[count] == '(')
                        level++;
                    else
                        level--;
                } while (level > 0);
            }
            else
            {
                do
                {
                    count--;

                    if (s[count] == ')')
                        level++;
                    else
                        level--;
                } while (level > 0);
            }

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