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.Linq;
using System.Collections.Generic;

class Mondai
{
    static void Main()
    {
        var S = Console.ReadLine();
        var mae = string.Empty;
        var ushiro = string.Empty;
        for (int i=0;i<4;++i)
        {
            if (i < 2) mae += S[i];
            else ushiro+= S[i];
        }
        var ans = "AMBIGUOUS";
        var maeNum = Int32.Parse(mae);
        var ushiroNum = Int32.Parse(ushiro);
        if ((12 < maeNum && 12 < ushiroNum) || (maeNum <= 0 && ushiroNum <= 0)) ans = "NA";
        else if (maeNum <= 0 || 12 < maeNum) ans = "YYMM";
        else if (ushiroNum <= 0 || 12 < ushiroNum) ans = "MMYY";
        Console.WriteLine(ans);
    }
}