using System;

class Program
{
    static void Main()
    {
        string[] s = Console.ReadLine().Split();
        int n = int.Parse(s[0]);
        int k = int.Parse(s[1]);
        char[] c = Console.ReadLine().ToCharArray();

        int a = 0;
        int b = 0;
        int ans = 0;

        if (c[k - 1] == '(')
        {
            a++;
            for (int i = k; ; i++)
            {
                if (c[i] == ')')
                {
                    b++;
                    if (a == b)
                    {
                        ans = k + 2 * a - 1;
                        break;
                    }
                }
                else a++;
            }
        }
        else
        {
            b++;
            for (int i = k - 2; ; i--)
            {
                if (c[i] == '(')
                {
                    a++;
                    if (a == b)
                    {
                        ans = k - 2 * a + 1;
                        break;
                    }
                }
                else b++;
            }
        }

        Console.WriteLine(ans);
    }
}