Problem:
Score : 100 points

Problem Statement

You are given an integer N that has exactly four digits in base ten.
How many times does 2 occur in the base-ten representation of N?

Constraints

1000 \leq N \leq 9999

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer.

Sample Input 1

1222

Sample Output 1

3

2 occurs three times in 1222. By the way, this contest is held on December 22 (JST).

Sample Input 2

3456

Sample Output 2

0

Sample Input 3

9592

Sample Output 3

1

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string str = Console.ReadLine();

        int[] a = new int[4];

        int count = 0;
        for(int i = 0; i < 4; i++)
        {
            a[i] = str[i] - '0';
            if (a[i] == 2) count++;
        }
        //数値変換完了

        Console.WriteLine(count);
    }
}