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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.*;
import java.util.StringTokenizer;

public class Main {

  private void solve(InputReader in, PrintWriter out) {
    String s = in.next();
    int count = 0;
    for (char c : s.toCharArray()){
      if (c == '2') count++;
    }
    out.println(count);
  }

  private static int gcd(int n, int m) {
    return m == 0 ? n : gcd(m, n % m);
  }


  public static void main(String[] args) {
    new Main().run();
  }

  private void run() {

    try (InputReader in = new InputReader(System.in);
         PrintWriter out = new PrintWriter(System.out)) {
      solve(in, out);
    }
  }


  static class InputReader implements AutoCloseable {
    private BufferedReader reader;
    private StringTokenizer tokenizer;

    InputReader(InputStream stream) {
      //reader = new BufferedReader(new FileReader(stream), 32768);
      reader = new BufferedReader(new InputStreamReader(stream), 32768);
      tokenizer = null;
    }

    String next() {
      while (tokenizer == null || !tokenizer.hasMoreTokens()) {
        try {
          tokenizer = new StringTokenizer(reader.readLine());
        } catch (IOException e) {
          throw new RuntimeException(e);
        }
      }
      return tokenizer.nextToken();
    }

    public int nextInt() {
      return Integer.parseInt(next());
    }

    public long nextLong() {
      return Long.parseLong(next());
    }

    public double nextDouble() {
      return Double.parseDouble(next());
    }

    @Override
    public void close() {
    }
  }

}