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 OCaml (4.02.3) (judge verdict: Accepted)

let n = read_line ()
let f x s = let n = ref 0 in String.iter (fun c -> if c = x then incr n) s; !n
let _ = Printf.printf "%d\n" @@ f '2' n