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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php

fscanf(STDIN, "%s", $s);

function isMM($str) {
    switch ($str) {
        case '01':
        case '02':
        case '03':
        case '04':
        case '05':
        case '06':
        case '07':
        case '08':
        case '09':
        case '10':
        case '11':
        case '12':
            return true;
        default:
            return false;
    }
}

$first = substr($s, 0, 2);
$last = substr($s, 2);

$is_yymm = isMM($last);
$is_mmyy = isMM($first);

if ($is_yymm && $is_mmyy) {
    echo 'AMBIGUOUS';
} else if ($is_yymm) {
    echo 'YYMM';
} else if ($is_mmyy) {
    echo 'MMYY';
} else {
    echo 'NA';
}