#include <iostream>
#include <string.h>
#include <string>
using namespace std;

int main() {
	
	string table = "abcdefghijklmnopqrstuvwxyz.?! ",s,t;
	int i,l;
	
	while(cin>>s){
		l=s.length();
		t="";
		
		if(l%2)
			cout<<"NA";
		else{
			for(i=0;i<l;i+=2){
				if(s[i]<=54 && s[i]>=49 && s[i+1]<=53 && s[i+1]>=49)
					t += table[(s[i]-49)*5+s[i+1]-49];
				else{
					t="NA";break;
				}
			}
			cout<<t;
		}
			
		cout<<endl;
	}
	return 0;
}