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.Threading.Tasks;

namespace abc119d
{
    class Program
    {
        static void Main(string[] args)
        {
            var S = ReadInt();
            bool YYMM = false;
            bool MMYY = false;

            int u = S / 100;
            int d = S % 100;

            // YYMM 
            if (u >= 1 && u <= 99)
                if (d >= 1 && d <= 12)
                    YYMM = true;
            //MMYY
            if (u >= 1 && u <= 12)
                if (d >= 1 && d <= 99)
                    MMYY = true;
            if (YYMM && MMYY)
                Console.WriteLine("AMBIGUOUS");
            else if (YYMM)
                Console.WriteLine("YYMM");
            else if (MMYY)
                Console.WriteLine("MMYY");
            else
                Console.WriteLine("NA");

#if DEBUG
            Console.ReadKey();
#endif
        }

        private static bool IsRange(int a, int from, int to) => (from <= a && a <= to);
        private static int ReadInt() => int.Parse(Console.ReadLine());
        private static List<int> ReadIntList() => Console.ReadLine().Split().Select(int.Parse).ToList();
        private static double ReadDouble() => double.Parse(Console.ReadLine());
        private static List<double> ReadDoubleList() => Console.ReadLine().Split().Select(double.Parse).ToList();
        private static long ReadLong() => long.Parse(Console.ReadLine());
        private static List<long> ReadLongList() => Console.ReadLine().Split().Select(long.Parse).ToList();
        private static List<int> Int2Digits(int a) => a.ToString().ToCharArray().Select(_ => int.Parse(_.ToString())).ToList();
        private static int BinarySearch<Type>(IReadOnlyList<Type> s, Type target) // target 以下の最大要素のインデックスを返す
            where Type : IComparable
        {
            var lower = 0;
            var upper = s.Count - 1;
            while (upper - lower > 1)
            {
                var mid = lower + (upper - lower) / 2;
                if (s[mid].CompareTo(target) <= 0)
                {
                    lower = mid;
                }
                else
                {
                    upper = mid;
                }

            }
            return lower;
        }
    }
}