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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>

int main(void) {

	char s[4];
	char head[2], tail[2];
	int  mmyy = 0;
	scanf("%s", &s);
	for (int i = 0; i < 2; i++) {
		head[i] = s[i];
		tail[i] = s[i + 2];
	}

	if (head[0] == '0')	mmyy++;
	else if (head[1] == '1' && (head[1] == '0' || head[1] == '1' || head[1] == '2'))
		mmyy++;
	if (mmyy == 1) {
		if (tail[0] == '0')	printf("AMBIGUOUS");
		else if (tail[1] == '1' && (tail[1] == '0' || tail[1] == '1' || tail[1] == '2'))
			printf("AMBIGUOUS");
		else
			printf("MMYY");
	}
	else {
		if (tail[0] == '0')	printf("YYMM");
		else if (tail[1] == '1' && (tail[1] == '0' || tail[1] == '1' || tail[1] == '2'))
			printf("YYMM");
		else printf("NA");
	}

	return 0;
}