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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;

namespace AtCoder.Question
{
    public class QuestionB
    {
        public static void Main(string[] args)
        {
            var date = ReadHelper.ReadValue<string>();
            var a = int.Parse(date.Substring(0, 2));
            var b = int.Parse(date.Substring(2, 2));

            if (0 < a && a <= 12)
            {
                if (0 < b && b <= 12)
                {
                    Console.WriteLine("AMBIGUOUS");
                }
                else
                {
                    Console.WriteLine("MMYY");
                }
            }
            else
            {
                if (0 < b && b <= 12)
                {
                    Console.WriteLine("YYMM");
                }
                else
                {
                    Console.WriteLine("NA");
                }
            }
        }

        static class ReadHelper
        {
            internal static T ReadValue<T>()
            {
                return (T)Convert.ChangeType(Console.ReadLine(), typeof(T));
            }
            internal static (T1, T2) ReadValue<T1, T2>()
            {
                var input = Console.ReadLine().Split(' ');
                return ((T1)Convert.ChangeType(input[0], typeof(T1)), (T2)Convert.ChangeType(input[1], typeof(T2)));
            }
            internal static (T1, T2, T3) ReadValue<T1, T2, T3>()
            {
                var input = Console.ReadLine().Split(' ');
                return ((T1)Convert.ChangeType(input[0], typeof(T1)), (T2)Convert.ChangeType(input[1], typeof(T2)), (T3)Convert.ChangeType(input[2], typeof(T3)));
            }
            internal static (T1, T2, T3, T4) ReadValue<T1, T2, T3, T4>()
            {
                var input = Console.ReadLine().Split(' ');
                return ((T1)Convert.ChangeType(input[0], typeof(T1)), (T2)Convert.ChangeType(input[1], typeof(T2)), (T3)Convert.ChangeType(input[2], typeof(T3)), (T4)Convert.ChangeType(input[3], typeof(T4)));
            }
            internal static T[] ReadValues<T>()
            {
                var input = Console.ReadLine().Split(' ');
                return input.Select(x => (T)Convert.ChangeType(x, typeof(T))).ToArray();
            }
        }

        static class MathAlgorithm
        {
            internal static bool IsPrime(long n)
            {
                if (n == 2) return true;
                if (n < 2 || n % 2 == 0) return false;
                var sqrt = Math.Sqrt(n);
                for (int i = 3; i <= sqrt; i += 2) if (n % i == 0) return false;
                return true;
            }
            internal static IEnumerable<long> EnumeratePrimes(long n)
            {
                var i = 2L;
                while (i * i <= n)
                {
                    if (n % i == 0)
                    {
                        n /= i;
                        yield return i;
                    }
                    else
                    {
                        i += i == 2 ? 1 : 2;
                    }
                }
                if (n != 1) yield return n;
            }
        }
    }
}