using System;
using System.Linq;

class No22
{
    static void Main()
    {
        var num = Console.ReadLine().Split(' ').Select(x => Int32.Parse(x)).ToArray();
        var line = Console.ReadLine().ToCharArray();
        var isAdd = line[num[1] - 1] == '(' ? true : false;
        var i = isAdd ? 0 : line.Length - 1;
        var firstChar = isAdd ? line[0] : line[line.Length - 1];
        var beforeChar = firstChar;
        var shindo = 1;
        var myShindo = ((isAdd && num[1] == 1) || (!isAdd && num[1] == line.Length)) ? 1 : 0;
        while (true)
        {
            i = isAdd ? i + 1 : i - 1;
            if (line[i] == beforeChar)
            {
                if (line[i] == firstChar) shindo++;
                else shindo--;
            }
            if (i + 1 == num[1]) myShindo = shindo;
            if (isAdd)
            {
                if (shindo == myShindo && line[i] == ')') break;
            }
            else
            {
                if (shindo == myShindo && line[i] == '(') break;
            }
            beforeChar = line[i];
        }
        Console.WriteLine(i + 1);
    }
}