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 Ruby (2.3.3) (judge verdict: Accepted)

S = gets.chomp

class Object
  def yield_self
    yield(self)
  end
end

def is_probably_month?(i)
  return i > 0 && i < 13
end

puts begin
  S.yield_self do |s|
    break "NA" unless S =~ /^[0-9]{4}$/
    head, tail = [ s[0..1], s[2..3] ].map(&:to_i)
    break "AMBIGUOUS" if is_probably_month?(head) && is_probably_month?(tail)
    break "MMYY" if is_probably_month?(head)
    break "YYMM" if is_probably_month?(tail)
    "NA"
  end
end