using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

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

            bool mode;
            int cnt = 0;
            int i = k - 1;

            mode = s[k - 1].Equals('(') ? true : false;

            while (i >= 0 && i < n)
            {
                if (s[i].Equals(s[k - 1])) cnt++;
                else cnt--;

                if (cnt == 0)
                {
                    break;
                }
                else
                {
                    if (mode) i++;
                    else i--;
                }
            }
            Console.WriteLine(i + 1);
        }
    }
}