#include <bits/stdc++.h>
using namespace std;
int main() {
	string str;
	char poke[6][6]={{"abcde"},{"fghij"},{"klmno"},{"pqrst"},{"uvwxy"},{"z.?! "}};
	while(cin>>str){
		if(str.size()%2!=0)cout<<"NA"<<endl;
		else {
			string ans;
			bool kawa=0;
			for(int i=1;i<str.size();i+=2){
				if(str[i-1]-'1'<0||str[i-1]-'1'>5||str[i]-'1'<0||str[i]-'1'>4){
					kawa=1;
					break;
				}
				else ans+=poke[str[i-1]-'1'][str[i]-'1'];
			}
			if(kawa)cout<<"NA"<<endl;
			else cout<<ans<<endl;
		}
	}
	return 0;
}