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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Linq;

namespace B___YYMM_or_MMYY
{
    class Program
    {
        static void Main(string[] args)
        {
            var S = Console.ReadLine();

            int AA = int.Parse(new string(S.Where((e, i) => i < 2).ToArray()));
            int BB = int.Parse(new string(S.Where((e, i) => 2 < i).ToArray()));

            if (MM(AA) && YY(BB))
                Console.WriteLine(YY(AA) && MM(BB) ? "AMBIGUOUS" : "MMYY");
            else if (YY(AA) && MM(BB))
                Console.WriteLine("YYMM");
            else
                Console.WriteLine("NA");
        }

        static bool MM(int XX) => 1 <= XX && XX <= 12;
        static bool YY(int XX) => 0 <= XX && XX <= 99;
    }
}