#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;
int main()
{
	int i;
	char c, d, s[201], r[101], t[5][7] = {"afkpuz", "bglqv.", "chmrw?", "dinsx!", "ejoty "};
	while (cin >> s)
	{
		if (cin.eof()) break;
		if (strlen(s)%2 == 0)
		{
			for (i = 0; i < strlen(s); i += 2)
			{
				c = s[i], d = s[i+1];
				if (atoi(&c) > 6 || atoi(&d) > 5)
				{
					cout << "NA" << endl;
					break;
				}
				r[i/2] = t[atoi(&d)-1][atoi(&c)-1];
			}
			if (atoi(&c) > 6 || atoi(&d) > 5)
				continue;
			r[i/2] = '\0';
			cout << r << endl;
		}
		else
			cout << "NA" << endl;
	}
}