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.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();

        string A = S.Substring(0, 2);
        string B = S.Substring(2, 2);

        int a = int.Parse(A);
        int b = int.Parse(B);

        if ((a == 0 || a > 12) && (b == 0 || b > 12))
        {
            Console.WriteLine("NA");
            return;
        }

        if (a <= 12 && b <= 12)
        {
            Console.WriteLine("AMBIGUOUS");
        }
        else if (a <= 12)
        {
            Console.WriteLine("MMYY");            
        }
        else if (b <= 12)
        {
            Console.WriteLine("YYMM");
        }
    }

    static long calcGCD(long num1, long num2)
    {
        if(num1 < num2)
        {
            var tmp = num1;
            num1 = num2;
            num2 = tmp;
        }

        while(true)
        {
            long res;
            long div = Math.DivRem(num1, num2, out res);

            if (res == 0)
            {
                return num2;
            }
            else
            {
                num1 = num2;
                num2 = res;
            }
        }
    }
}


static class MathUtil
{
    public static T Max<T>(params T[] datas)
    {
        return datas.Max();
    }

    public static T Min<T>(params T[] datas)
    {
        return datas.Min();
    }

    public static IEnumerable<IEnumerable<int>> GetPermutation(int n)
    {
        if (n == 0)
        {
            yield return Single(0);
            yield break;
        }

        for (int i = 0; i <= n; i++)
        {
            foreach (var x in GetPermutation(n - 1))
            {
                yield return Single(i).Concat(x.Select(itm => itm < i ? itm : itm + 1));
            }
        }
    }

    private static IEnumerable<int> Single(int x)
    {
        yield return x;
    }

    public static IEnumerable<int> EnumeratePrimeNumbers()
    {
        List<int> primes = new List<int>() { 2 };
        yield return 2;

        for (int i = 3; i < int.MaxValue; i++)
        {
            bool isPrime = true;
            int Sqrt = (int)Math.Sqrt(i) + 1;

            foreach (var prime in primes)
            {
                if (prime > Sqrt)
                {
                    break;
                }
                if (i % prime == 0)
                {
                    isPrime = false;
                    break;
                }
            }

            if (isPrime)
            {
                primes.Add(i);
                yield return i;
            }
        }
    }
}