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;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            int numberof2 = 0;
            var integer = int.Parse(Console.ReadLine());
            if (integer < 1000 || 9999 < integer)
            {
                Console.WriteLine("ERROR: Please input the number from 1000 to 9999.");
                return;
            }
            for (var digit = 0; digit < 4; digit++)
            {
                if (integer % 10 == 2)
                {
                    numberof2++;
                }
                integer /= 10;
            }
            Console.WriteLine("{0}", numberof2);
        }
    }
}