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)

#!/usr/bin/env php
<?php
const YYMM = 'YYMM';
const MMYY = 'MMYY';
const BOTH = 'AMBIGUOUS';
const INVALID = 'NA';
function genInputs() {
    while(($input = rtrim(fgets(STDIN))) !== false) {
        foreach (explode(' ', $input) as $v) {
            yield $v;
        }
    }
}
function getNext($gen) {
    $value = $gen->current();
    $gen->next();
    return $value;
}
$gen = genInputs();

$S = (int)getNext($gen);

$a = (int)($S / 100);
$b = (int)($S % 100);


function valid_month($n) {
    return ($n >= 1 && $n <= 12);
}

if (valid_month($a) && valid_month($b)) {
    echo BOTH;
} elseif (valid_month($a)) {
    echo MMYY;
} elseif (valid_month($b)) {
    echo YYMM;
} else {
    echo INVALID;
}
echo PHP_EOL;