#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)
int main(){
	string data[5]={"afkpuz","bglqv.","chmrw?","dinsx!","ejoty "};
	string s;
	while(cin>>s){
		bool f=false;
		if(s.size()%2!=0){
			cout<<"NA"<<endl;
			continue;
		}
		for(int i=0;i<s.size();i+=2)if(s[i]>'6'||s[i]<'1'||s[i+1]>'5'||s[i]<'1')f=true;
		if(f||s.size()%2==1){
			cout<<"NA"<<endl;
		}else{
			for(int i=0;i<s.size();i+=2)cout<<data[s[i+1]-'0'-1][s[i]-'0'-1];
			cout<<endl;
		}
	}
}