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;

namespace ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
          	var input_B = Console.ReadLine()
                .ToCharArray().Select(i => int.Parse(i.ToString())).ToArray();
            var isMMYY_M0 = Regex.IsMatch(input_B[1].ToString(), @"[1-9]+$");
            var isMMYY_M1 = Regex.IsMatch(input_B[1].ToString(), @"[0-2]+$");
            var isYYMM_M0 = Regex.IsMatch(input_B[3].ToString(), @"[1-9]+$");
            var isYYMM_M1 = Regex.IsMatch(input_B[3].ToString(), @"[0-2]+$");

            var isMMYY = false;
            var isYYMM = false;
            if ((input_B[0] == 0 && isMMYY_M0) || (input_B[0] == 1 && isMMYY_M1))
                isMMYY = true;

            if ((input_B[2] == 0 && isYYMM_M0) || (input_B[2] == 1 && isYYMM_M1))
                isYYMM = true;

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