#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)
int main(){
	char data[6][6]={"abcde","fghij","klmno","pqrst","uvwxy","z.?! "};
	string s;
	while(cin>>s){
		string ans;
		if(s.size()%2!=0){
			cout<<"NA"<<endl;
			continue;
		}
		for(int i=0;i<s.size();i+=2){
			int x=s[i]-'1',y=s[i+1]-'1';
			if(x<0||x>=6||y<0||y>=5){
				cout<<"NA"<<endl;
				continue;
			}
			ans+=data[x][y];
		}
		cout<<ans<<endl;
	}
}