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: Wrong Answer)

package main

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

// ----------------------------------------------------------------

func main() {
	var s string
	fmt.Scan(&s)

	y, _ := strconv.Atoi(string(s[:2]))
	m, _ := strconv.Atoi(string(s[2:]))

	if y == 0 || m == 0 {
		if y == 0 {
			if m >= 1 && m <= 12 {
				fmt.Println("YYMM")
			} else {
				fmt.Println("NA")
			}
		} else if m == 0 {
			if y >= 1 && y <= 12 {
				fmt.Println("MMYY")
			} else {
				fmt.Println("NA")
			}
		}
	} else {
		if (y >= 1 && y <= 12) && (m >= 1 && m <= 12) {
			fmt.Println("AMBIGUOUS")
		}
		if (y >= 1 && y <= 12) && (m < 1 || m > 12) {
			fmt.Println("MMYY")
		}
		if (y < 1 || y > 12) && (m >= 1 && m <= 12) {
			fmt.Println("YYMM")
		}
	}

}

// ----------------------------------------------------------------

var dx = []int{0, 1, 0, -1, 0}
var dy = []int{1, 0, -1, 0, 0}
var inf = int(1e9)

func pow(a, b int) int {
	return int(math.Pow(float64(a), float64(b)))
}

func lcm(a, b int) int {
	return a * b / gcd(a, b)
}

func gcd(a, b int) int {
	if a < b {
		a, b = b, a
	}
	for b != 0 {
		a, b = b, a%b
	}
	return a
}

func max(a ...int) int {
	r := a[0]
	for i := 0; i < len(a); i++ {
		if r < a[i] {
			r = a[i]
		}
	}
	return r
}

func min(a ...int) int {
	r := a[0]
	for i := 0; i < len(a); i++ {
		if r > a[i] {
			r = a[i]
		}
	}
	return r
}

func sum(a []int) (r int) {
	for i := range a {
		r += a[i]
	}
	return r
}

func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}

type pair struct {
	a, b int
}

type pairs []pair

func (p pairs) Len() int {
	return len(p)
}

func (p pairs) Swap(i, j int) {
	p[i], p[j] = p[j], p[i]
}

func (p pairs) Less(i, j int) bool {
	if p[i].a == p[j].a {
		return p[i].b < p[j].b
	}
	return p[i].a < p[j].a
}

var nextReader func() []byte

func init() {
	nextReader = newScanner()
	log.SetFlags(log.Lshortfile)
}

func newScanner() func() []byte {
	r := bufio.NewScanner(os.Stdin)
	r.Buffer(make([]byte, 1024), int(1e+11))
	r.Split(bufio.ScanWords)
	return func() []byte {
		r.Scan()
		return r.Bytes()
	}
}

func nextBytes() []byte {
	return nextReader()
}

func nextString() string {
	return string(nextReader())
}

func nextInt64() int64 {
	v, _ := strconv.ParseInt(string(nextReader()), 10, 64)
	return v
}

func nextInt() int {
	v, _ := strconv.Atoi(string(nextReader()))
	return v
}

func nextInts(n int) []int {
	r := make([]int, n)
	for i := 0; i < n; i++ {
		r[i] = nextInt()
	}
	return r
}

func nextFloat64() float64 {
	f, _ := strconv.ParseFloat(string(nextReader()), 64)
	return f
}