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.util.Scanner;
import java.util.regex.Pattern;

public class Main {

	public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    String S = sc.next();

    String mae = S.substring(0, 2);
    String ato = S.substring(2, 4);

    boolean maet = false;
    boolean atot = false;

    Pattern nump = Pattern.compile("[0-9]{2}");
    if (nump.matcher(mae).find() && nump.matcher(ato).find()) {
    	// YYMMorMMYYどちらか
    	if (mae.equals("01") || mae.equals("02") || mae.equals("03") || mae.equals("04") ||
    			mae.equals("05") || mae.equals("06") || mae.equals("07") || mae.equals("08") ||
    			mae.equals("09") || mae.equals("10") || mae.equals("11") || mae.equals("12")) {
    		maet = true;
    	}
    	if (ato.equals("01") || ato.equals("02") || ato.equals("03") || ato.equals("04") ||
    			ato.equals("05") || ato.equals("06") || ato.equals("07") || ato.equals("08") ||
    			ato.equals("09") || ato.equals("10") || ato.equals("11") || ato.equals("12")) {
    		atot = true;
    	}
    	if (maet && atot) {
    		System.out.println("AMBIGUOUS");
    	} else if (maet && !atot) {
    		System.out.println("MMYY");
    	} else if (!maet && atot) {
    		System.out.println("YYMM");
    	} else {
    		System.out.println("NA");
    	}
    } else {
    	// どちらでもない
    	System.out.println("NA");
    }

  }

}