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 Haskell (GHC 7.10.3) (judge verdict: Accepted)

main = do
    n <- getLine
    print $ solve 0 n

solve :: Int -> String -> Int
solve ac []         = ac
solve ac ('2':xs)   = solve (ac+1)  xs
solve ac (x:xs)     = solve  ac     xs