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: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

using System.Collections;

class Program
{
    static void Main()
    {
        string S = Console.ReadLine();

        if (canBeMMYY(S) && canBeYYMM(S))
        {
            Console.WriteLine("AMBIGUOUS");
        }
        else if (canBeMMYY(S))
        {
            Console.WriteLine("MMYY");
        }
        else if (canBeYYMM(S))
        {
            Console.WriteLine("YYMM");
        }
        else
        {
            Console.WriteLine("NA");
        }
        
    }

    static bool canBeYYMM(string s)
    {
        int left = int.Parse(s.Substring(0, 2));
        int right = int.Parse(s.Substring(2, 2));

        if (1 <= right && right <= 12)
        {
            return true;
        }
        else return false;
    }

    static bool canBeMMYY(string s)
    {
        int left = int.Parse(s.Substring(0, 2));
        int right = int.Parse(s.Substring(2, 2));

        if (1 <= left && left <= 12)
        {
            return true;
        }
        else return false;
    }
}