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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class Main {

  private static final String[] MM = {"01", "02", "03", "04", "05", "06", "07", "08", "09", "10", "11", "12"};

  public static void main(String[] args) {

    String sDate = null;
    try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in))) {
      sDate = br.readLine();
    } catch (IOException e) {
      e.printStackTrace();
      System.exit(1);
    }

    String numOne = sDate.substring(0, 2);
    String numTwo = sDate.substring(2, 4);

    boolean isOne = false;
    boolean isTwo = false;

    for (int i = 0; i < MM.length; i++) {

      if (isOne == false && MM[i].equals(numOne)) {
        isOne = true;
      }

      if (isTwo == false && MM[i].equals(numTwo)) {
        isTwo = true;
      }
    }

    if (isOne && isTwo) {
      System.out.print("AMBIGUOUS");
    } else if (isOne == false && isTwo == false) {
      System.out.print("NA");
    } else if (isOne) {
      System.out.print("MMYY");
    } else if (isTwo) {
      System.out.print("YYMM");
    }
  }
}