#include<iostream>
#include<string>
using namespace std;
int main() {
	const char r[6][5] = { {'a','b','c','d','e'} ,{'f','g','h','i','j'},{'k','l','m','n','o'},{'p','q','r','s','t'},{'u','v','w','x','y'},{'z','.','?','!',' '} };
	string s;
	while (cin >> s){
		string str;
		bool b = true;
		if (s.size() % 2 == 1) { b = false; }
		else for (int i = 0; i < s.size(); i += 2) {
			int a, bc;
			a = s[i] - '0';
			bc = s[i + 1] - '0';
			if (a >= 7 || bc >= 6){
				b = false;
			}
			else str += r[a - 1][bc - 1];
		}
		if (b){
			cout << str << endl;
		}
		else cout << "NA" << endl;
	}
}