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

int main() {
	string abc = "abcdefghijklmnopqrstuvwxyz.?! ";
	string b;
	while (cin >> b) {
		if (b.size() % 2 != 0) {
			cout << "NA" << endl;
		} else {
			for (int i = 0; i < b.size(); i++) {
				int p = b[i] - '0';
				int q = b[i+1] - '0';
				cout << abc[5*(p-1)+q-1];
				i++;
			}
			cout << endl;
		}
	}
	return 0;
}