Problem:
﻿Score: 300 points

Problem Statement

Mr. Infinity has a string S consisting of digits from 1 to 9. Each time the date changes, this string changes as follows:

Each occurrence of 2 in S is replaced with 22. Similarly, each 3 becomes 333, 4 becomes 4444, 5 becomes 55555, 6 becomes 666666, 7 becomes 7777777, 8 becomes 88888888 and 9 becomes 999999999. 1 remains as 1.

For example, if S is 1324, it becomes 1333224444 the next day, and it becomes 133333333322224444444444444444 the day after next.
You are interested in what the string looks like after 5 \times 10^{15} days. What is the K-th character from the left in the string after 5 \times 10^{15} days?

Constraints

S is a string of length between 1 and 100 (inclusive).

K is an integer between 1 and 10^{18} (inclusive).

The length of the string after 5 \times 10^{15} days is at least K.

Input

Input is given from Standard Input in the following format:

S
K

Output

Print the K-th character from the left in Mr. Infinity's string after 5 \times 10^{15} days.

Sample Input 1

1214
4

Sample Output 1

2

The string S changes as follows:

Now: 1214

After one day: 12214444

After two days: 1222214444444444444444

After three days: 12222222214444444444444444444444444444444444444444444444444444444444444444

The first five characters in the string after 5 \times 10^{15} days is 12222. As K=4, we should print the fourth character, 2.

Sample Input 2

3
157

Sample Output 2

3

The initial string is 3. The string after 5 \times 10^{15} days consists only of 3.

Sample Input 3

299792458
9460730472580800

Sample Output 3

2

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;

namespace ABC106C
{
    class MainClass
    {
        public static void Main(string[] args)
        {

            // N M みたいな入力
            string Sinput = Console.ReadLine();
            char[] S = Sinput.ToCharArray();

            // N M みたいな入力
            string input2 = Console.ReadLine();
            long K = long.Parse(input2);

            //5000兆
            long n = 50000000000000000;

            //ans
            int ans = 0;

            for (int i = 0; i < S.Length;i++){

                if((n*Math.Log10(int.Parse(S[i].ToString())))>K){
                    ans = int.Parse(S[i].ToString());
                    break;
                }else{
                    K =  K - (long)(n * Math.Log10(int.Parse(S[i].ToString())) + 1);
                    //Console.WriteLine(K);
                }

            }


            //出力
            Console.WriteLine(ans);
        }
    }
}