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: Wrong Answer)

import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String A = sc.next();
    boolean B = isYYMM(A);
    boolean C = isMMYY(A);
    if (B & C) {
      System.out.println("AMBIGUOUS");
    } else if (B) {
      System.out.println("YYMM");
    } else if (C) {
      System.out.println("MMYY");
    } else {
      System.out.println("NA");
    }
  }

  private static boolean isYYMM(String num) {
    String YY = num.substring(0, 2);
    String MM = num.substring(2, 4);
    int newYY = Integer.parseInt(YY);
    int newMM = Integer.parseInt(MM);
    if (newYY != 00 && newMM >= 1 && newMM <= 12) {
      return true;
    } else {
      return false;
    }
  }

  private static boolean isMMYY(String num) {
    String MM = num.substring(0, 2);
    String YY = num.substring(2, 4);
    int newMM = Integer.parseInt(MM);
    int newYY = Integer.parseInt(YY);
    if (newYY != 00 && newMM >= 1 && newMM <= 12) {
      return true;
    } else {
      return false;
    }
  }
}