#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;
int main()
{
	int i, j = -1;
	char c, d, s[201], r[1024][101], t[5][7] = {"afkpuz", "bglqv.", "chmrw?", "dinsx!", "ejoty "};
	bool f;
	while (cin >> s)
	{
		if (cin.eof()) break;
		j++;
		if (strlen(s)%2 == 0)
		{
			for (i = f = 0; i < strlen(s); i += 2, f = 0)
			{
				c = s[i], d = s[i+1];
				if (atoi(&c) > 6 || atoi(&d) > 5)
				{
					strcpy(r[j], "NA");
					f = 1;
					break;
				}
				r[j][i/2] = t[atoi(&d)-1][atoi(&c)-1];
			}
			if (f)
				continue;
			r[j][i/2] = '\0';
		}
		else
			strcpy(r[j], "NA");
	}
	for (i = 0; i < j; i++)
		cout << r[i] << endl;
}