#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;
	}
}