#include <stdio.h> // C++???????????????
#include <string.h> // c++???????????????
#include <math.h> // c++???????????????
#include <iostream>
#include <string>
#include <stack>
#include <queue>
#include <map>
#include <algorithm>
using namespace std;

typedef long long int lli;
#define PI 3.1415926535897932
#define N 100
#define MAX(a,b) ((a>b)?(a):(b)) // ?????§????????????
#define MIN(a,b) ((a<b)?(a):(b)) // ????°?????????????
#define INRANGE(a,b,c) ((a<=b&&b<=c)?(1):(0)) // a<=b<=c??????????????????????????????


void swap(int &a, int &b) { // c??????*
	int w = a;
	a = b;
	b = w;
}

int getdigit(int num) { // ??´??°????????°?????????
	int i, j;
	if (num<0) num *= -1; // ?????°???????????¢
	if (num == 0)return 1;
	for (i = 10, j = 1;; i *= 10, j++) {
		if (INRANGE(i / 10, num, i - 1))return j;
	}
	return 0; // ????????¨??????
}

int getN(int num, int digit) {
	int i = 1, j;
	for (j = 1; j<digit; i *= 10, j++);
	return (num / i) % 10;
}

int zeller(int y, int m, int d) { // 0????????\????????§??????
	if (m<3) { y--; m += 12; }
	return (y + y / 4 - y / 100 + y / 400 + (13 * m + 8) / 5 + d) % 7;
}

int gcd(int a, int b) {	// ?????§??¬?´???°
	if (b == 0) return a;
	return gcd(b, a%b);
}

int lcm(int a, int b) {	// ????°???¬?????°
	return a*b / gcd(a, b);
}

int stoi(const string str) { // ?????????????????´??°
	int i = 0, j;
	int len = str.length();
	int w = 0;
	for (i = 1, j = 1; i <= len && INRANGE('0', str[len - i], '9'); i++, j *= 10) {
		w += (str[len - i] - '0')*j;
	}
	if (str[0] == '-')w *= -1;
	return w;
}

string itos(int a) { // ??´??°???????????????
	int i;
	string str = "";
	int keta;
	if (a<0) { str += '-'; a *= -1; } // ?????°??????????????????
	for (keta = 10; a / keta != 0; keta *= 10);
	for (i = keta / 10; i != 0; i /= 10) {
		str += ((a / i) % 10) + '0';
	}
	return str;
}

char kaezi[100][100] = { {"XXXXXXX"},{"Xabcde"},{"Xfghij"},{"Xklmno"},{"Xpqrst"},{"Xuvwxy"},{"Xz.?! "} };

int main(void) {
	string str;
	string det;
	int i, j;
	while (cin>>str) {
		det = "";
		for (i = 0; i < str.length(); i+=2) {
			if (str.length() % 2 == 1) { det = "NA"; break; }
			if (INRANGE('1', str[i], '6') && INRANGE('1', str[i + 1], '5')) {
				det += kaezi[str[i] - '0'][str[i + 1] - '0'];
			}
			else {
				det = "NA"; break;
			}
		}
		cout << det << endl;

	}
	return 0;
}