#include <iostream>
#include <string>
using namespace std;

string s, r;

inline int cast(char c) {
	return (int)(c - '0');
}

int main(){
	bool fg;
	int a, b;
	while (cin >> s) {
		fg = false;
		r = "";
		if (s.size() % 2 != 0) {
			cout << "NA" << endl;
			continue;
		}
		for (int i = 0; i < s.size(); i += 2) {
			a = cast(s[i]), b = cast(s[i + 1]);
			if (a > 6 || b > 5 || a < 1 || b < 1) {
				fg = true;
				break;
			}
			if (a < 6) {
				r += ('a' + ((a - 1) * 5 + (b - 1)));
			}
			else {
				switch (b) {
				case 1:r += 'z';
					break;
				case 2:r += '.';
					break;
				case 3:r += '?';
					break;
				case 4:r += '!';
					break;
				case 5:r += ' ';
					break;
				default:break;
				}
			}
		}
		if (fg) {
			cout << "NA" << endl;
		}
		else {
			cout << r << endl;
		}
	}

	return 0;
}