using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    public void Solve()
    {
        int[] NK = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
        char[] S = Console.ReadLine().ToArray();

        int search = 1;
        int i;
        if ('('.Equals(S[NK[1] - 1]))
        {
            for (i = NK[1]; i < NK[0]; i++)
            {
                if ('('.Equals(S[i])) search++;
                if (')'.Equals(S[i])) search--;

                if (search == 0) break;
            }
        }
        else
        {
            for (i = NK[1] - 2; 0 < i; i--)
            {
                if (')'.Equals(S[i])) search++;
                if ('('.Equals(S[i])) search--;

                if (search == 0) break;
            }
        }

        Console.WriteLine(i + 1);
    }

    static void Main()
    {
        var solver = new Program();
        solver.Solve();
    }
}