Problem:
Score : 200 points

Problem Statement

You have a digit sequence S of length 4. You are wondering which of the following formats S is in:

YYMM format: the last two digits of the year and the two-digit representation of the month (example: 01 for January), concatenated in this order

MMYY format: the two-digit representation of the month and the last two digits of the year, concatenated in this order

If S is valid in only YYMM format, print YYMM; if S is valid in only MMYY format, print MMYY; if S is valid in both formats, print AMBIGUOUS; if S is valid in neither format, print NA.

Constraints

S is a digit sequence of length 4.

Input

Input is given from Standard Input in the following format:

S

Output

Print the specified string: YYMM, MMYY, AMBIGUOUS or NA.

Sample Input 1

1905

Sample Output 1

YYMM

May XX19 is a valid date, but 19 is not valid as a month. Thus, this string is only valid in YYMM format.

Sample Input 2

0112

Sample Output 2

AMBIGUOUS

Both December XX01 and January XX12 are valid dates. Thus, this string is valid in both formats.

Sample Input 3

1700

Sample Output 3

NA

Neither 0 nor 17 is valid as a month. Thus, this string is valid in neither format.

Solution in Haskell (GHC 7.10.3) (judge verdict: Accepted)

import Control.Applicative

main = do
  s <- getLine
  putStrLn $ case s of
    s
      | isMatchMonth first &&
        isMatchYear first &&
        isMatchMonth second &&
        isMatchYear second -> "AMBIGUOUS"
      | isMatchMonth first &&
        isMatchYear second -> "MMYY"
      | isMatchYear first &&
        isMatchMonth second -> "YYMM"
      | otherwise -> "NA"
      where
        first = read $ take 2 s
        second = read $ drop 2 s

isMatchMonth::Int -> Bool
isMatchMonth x
  | x <= 0 = False
  | x <= 12 = True
  | otherwise = False

isMatchYear::Int -> Bool
isMatchYear x
  | x < 0 = False
  | x <= 99 = True
  | otherwise = False