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.InputStreamReader;
import java.util.HashSet;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws Exception {
        Scanner scan = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
        String s = scan.next();
        boolean yymm = is_yymm(s);
        boolean mmyy = is_mmyy(s);
        String answer = "NA";
        if (yymm && mmyy) {
            answer = "AMBIGUOUS";
        } else if (yymm) {
            answer = "YYMM";
        } else if (mmyy) {
            answer = "MMYY";
        }
        System.out.println(answer);
    }
    public static boolean is_yymm(String s) throws Exception {
        return is_year(s.substring(0,2)) && is_month(s.substring(2,4));
    }
    public static boolean is_mmyy(String s) throws Exception {
        return is_month(s.substring(0,2)) && is_year(s.substring(2,4));
    }
    private static boolean is_month(String month) throws Exception {
        int x = Integer.parseInt(month, 10);
        if (x < 1) {
            return false;
        }
        if (12 < x) {
            return false;
        }
        return true;
    }
    private static boolean is_year(String month) throws Exception {
        int x = Integer.parseInt(month, 10);
        if (x < 0) {
            return false;
        }
        if (99 < x) {
            return false;
        }
        return true;
    }
}