#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <string>
#include <queue>
#include <stack>
#include <vector>
#include <sstream>

#define rep(x,to) for(int x=0;x<to;x++)
#define rep2(x,from,to) for(int x=from;x<to;x++)
typedef long long ll;

using namespace std;


int main(void){

string s[]={"abcde","fghij","klmno","pqrst","uvwxy","z.?! "};
string ind,res;
	while(cin >> ind){
		if(cin.eof()) break;
		res="";
		for(int i=0; i<ind.size(); i+=2){
			char s1=ind[i], s2=ind[i+1];
			if(s1<'1' | s1>'6' || s2<'1' || s2>'5' ){
				res = "NA";  break;
			}
			res += s[s1 - '0'- 1][s2 - '0'- 1];
		}
		cout << res << endl;
	}
	return 0;
	
}