#include<string>
#include<iostream>

using namespace std;

int main()
{
	char code[]="abcdefghijklmnopqrstuvwxyz.?! ";
	string s;
	while(cin>>s){
		if(s.length()%2==1)	cout<<"NA";
		else{
			for(int i=0;i<s.length();i+=2){
				int c=s[i]-'0'-1,r=s[i+1]-'0'-1;
				if(0<=c && c<=5 && 0<=r && r<=4){
					cout<<code[c*5+r];
				}
				else{
					cout<<"NA";
					break;
				}
			}
		}
		cout<<endl;
	}

	return 0;
}