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;

class Program {
    static void Main(string[] args) {
        //入力
        string str = Console.ReadLine();

        //カウンタ
        int ans = 0;

        //一文字ずつ判定
        for (int i = 0; i < str.Length; i++) {
            if (str[i] =='2') {
                ans++;
            }
        }

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