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);
    }
}