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 JavaScript (node.js v5.12) (judge verdict: Accepted)

"use strict";

const readData = input => {
  return {
    former: parseInt(input.substr(0, 2)),
    latter: parseInt(input.substr(2, 2))
  };
};

const mayBeMonth = n => n >= 1 && n <= 12;

const getType = data => {
  if (mayBeMonth(data.former)) {
    if (mayBeMonth(data.latter)) return "AMBIGUOUS";
    else return "MMYY";
  } else {
    if (mayBeMonth(data.latter)) return "YYMM";
    else return "NA";
  }
};

function Main(input) {
  let data = readData(input);
  console.log(getType(data));
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));