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           Data.List
main = getLine >>= putStrLn . f . (\(a, b) -> (read a, read b)) . splitAt 2
  where
    f :: (Int, Int) -> String
    f (a, b)
      | inMonth a && inMonth b =  "AMBIGUOUS"
      | not (inMonth a) && inMonth b =  "YYMM"
      | inMonth a && not (inMonth b) =  "MMYY"
      | otherwise = "NA"
    inMonth x = 1 <= x && x <= 12