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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func isMonth(n int) bool {
	return 1 <= n && n <= 12
}

func main() {

	stdin := bufio.NewScanner(os.Stdin)

	// 一行目
	stdin.Scan()
	line1 := stdin.Text()
	head, _ := strconv.Atoi(line1[0:2])
	tail, _ := strconv.Atoi(line1[2:4])

	if isMonth(head) && isMonth(tail) {
		fmt.Println("AMBIGUOUS")
	} else if isMonth(head) {
		fmt.Println("MMYY")
	} else if isMonth(tail) {
		fmt.Println("YYMM")
	} else {
		fmt.Println("NA")
	}
}