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;

namespace CSharpSample01
{
    
    class Program
    {

        

        static void Main(string[] args)
        {
            string S = Console.ReadLine();

            int s1 = int.Parse(S[0].ToString());
            int s2 = int.Parse(S[1].ToString());
            int s3 = int.Parse(S[2].ToString());
            int s4 = int.Parse(S[3].ToString());

            if(s1 >= 2)
            {
                //yymm
                if(s3 == 0)
                {
                    if(s4 != 0)
                    {
                        Console.WriteLine("YYMM");
                    }
                    else
                    {
                        Console.WriteLine("NA");
                    }
                }
                else if(s3 == 1)
                {
                    if(s4 <= 2)
                    {
                        Console.WriteLine("YYMM");
                    }
                    else
                    {
                        Console.WriteLine("NA");
                    }
                }
                else
                {
                    Console.WriteLine("NA");
                }
            }
            else if(s3 >= 2)
            {
                //mmyy
                if (s1 == 0)
                {
                    if (s2 != 0)
                    {
                        Console.WriteLine("MMYY");
                    }
                    else
                    {
                        Console.WriteLine("NA");
                    }
                }
                else if(s1 == 1)
                {
                    if(s2 <= 2)
                    {
                        Console.WriteLine("MMYY");
                    }
                    else
                    {
                        Console.WriteLine("NA");
                    }
                }
                else
                {
                    Console.WriteLine("NA");
                }
            }
            else
            {
                if(s1 == 1 && s3 == 1)
                {
                    if(s2 <= 2 && s4 <= 2)
                    {
                        Console.WriteLine("AMBIGUOUS");
                    }
                    else if(s2 <= 2)
                    {
                        Console.WriteLine("MMYY");
                    }
                    else if(s4 <= 2)
                    {
                        Console.WriteLine("YYMM");
                    }
                    else
                    {
                        Console.WriteLine("NA");
                    }
                }
                else if(s1 == 1 && s3 == 0)
                {
                    if(s2 > 2)
                    {
                        if(s4 != 0)
                        {
                            Console.WriteLine("YYMM");
                        }
                        else
                        {
                            Console.WriteLine("NA");
                        }                    
                    }
                    else if(s4 > 0)
                    {
                        Console.WriteLine("AMBIGUOUS");
                    }
                    else if(s4 == 0)
                    {
                        Console.WriteLine("MMYY");
                    }                  
                }
                else if(s1 == 0 && s3 == 1)
                {
                    if(s4 > 2)
                    {
                        if(s2 != 0)
                        {
                            Console.WriteLine("MMYY");
                        }
                        else
                        {
                            Console.WriteLine("NA");
                        }
                    }
                    else if(s2 > 0)
                    {
                        Console.WriteLine("AMBIGUOUS");
                    }
                    else if(s2 == 0)
                    {
                        Console.WriteLine("YYMM");
                    }                   
                }
                else
                {
                    if(s2 != 0 || s4 != 0)
                    {
                        Console.WriteLine("AMBIGUOUS");
                    }
                    else
                    {
                        Console.WriteLine("NA");
                    }                
                }
            }

            

        }
    }
}