#include<iostream>
using namespace std;
int main(){
	const 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','.','?','!',' '}};
	string s;
	while(cin>>s){
		string ans="";
		for(int i=0;i<s.size();i+=2){
			if(s[i]>='1'&&s[i]<='6'&&s[i+1]>='1'&&s[i+1]<='5'&&i+1<s.size()){
				ans+=TABLE[s[i]-'0'-1][s[i+1]-'0'-1];
			}else{
				ans="NA";
				break;
			}
		}
		cout<<ans<<"\n";
	}
	return 0;
}