#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <string>
#include <queue>
#include <vector>
#include <sstream>
#include <functional>
using namespace std;
char table[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','.','?','!',' '},
};
int main()
{
	string s;
    while(cin>>s){
		string ans="\0";
		if(!(s.length()%2)){
			for(int i=0;i<(int)s.length();i+=2){
				if('1'<=s[i]&&s[i]<='6'&&'1'<=s[i+1]&&s[i+1]<='5'){
					ans+=table[s[i]-'0'-1][s[i+1]-'0'-1];
				}else{
					ans="NA";
					break;
				}
			}
		}else{
			ans="NA";
		}
		cout<<ans<<endl;
	}
    return 0;
}