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;

namespace ConsoleApp2
{
	class Program
	{
		static void Main(string[] args)
		{
			string input = Console.ReadLine();
			int retval;
			if (!int.TryParse(input, out retval))
			{
				Console.WriteLine("NA");
				return;
			}

			string firstHalf = input.Substring(0, 2);
			bool isFirstMonth = IsMonthString(firstHalf);

			string latterHalf = input.Substring(2, 2);
			bool isLatterMonth = IsMonthString(latterHalf);

			if (isFirstMonth)
			{
				if (isLatterMonth)
				{
					Console.WriteLine("AMBIGUOUS");
					return;
				}
				else
				{
					Console.WriteLine("MMYY'");
					return;
				}
			}
			else
			{
				if (isLatterMonth)
				{
					Console.WriteLine("YYMM");
					return;
				}
				else
				{
					Console.WriteLine("NA");
					return;
				}
			}
		}

		static bool IsMonthString(string input)
		{
			int retval;
			if (!int.TryParse(input, out retval))
			{
				return false;
			}
			return 1 <= retval && retval <= 12;
		}
	}
}