#include <iostream>
#include <algorithm>
#include <string>

using namespace std;

int main ( void )
{
	string str;
	
	string hyo[] = { "abcde", "fghij", "klmno", "pqrst", "uvwxy", "z.?! " };
	
	while (cin >> str)
	{
		if (str.size() % 2)
		{
			cout << "NA" << endl;
			continue;
		}
		
		string out = "";
		
		for (int i = 0, len = str.size(); i < len; i+=2)
		{
			int x, y;
			
			y = str[i] - '1';
			x = str[i+1] - '1';
			
			out += hyo[y][x];
		}
		
		cout << out << endl;
	}
	
	return 0;
}