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;

namespace B
{
    class Program
    {
        static void Main(string[] args)
        {
            var S = Console.ReadLine();
            var s1 = int.Parse(S.Substring(0, 2));
            var s2 = int.Parse(S.Substring(2, 2));

            var isYYMM = s2 > 0 && s2 < 13;
            var isMMYY = s1 > 0 && s1 < 13;

            if (isYYMM)
            {
                if (isMMYY)
                {
                    Console.WriteLine("AMBIGUOUS");
                }
                else
                {
                    Console.WriteLine("YYMM");
                }
            }
            else
            {
                if (isMMYY)
                {
                    Console.WriteLine("MMYY");
                }
                else
                {
                    Console.WriteLine("NA");
                }
            }
        }

        static int NumberOfDigits(long x)
        {
            if (x < 10) return 1;

            var result = 0;
            while (x > 0)
            {
                result++;
                x /= 10;
            }

            return result;
        }

        static int SumOfDigits(int x)
        {
            var sum = 0;
            while (x > 0)
            {
                sum += x % 10;
                x /= 10;
            }

            return sum;
        }
    }
}