#include<bits/stdc++.h>
using namespace std;
int main(){
  string str[6]={"afkpuz","bglqv.","chmrw?"
		 ,"dinsx!","ejoty "};
  string str2;
  while(cin>>str2){
    if(str2.size()%2==1)
      cout<<"NA"<<endl;
    else{
      string ans="";
      for(int i=0;i<str2.size();i+=2){
	if(str2[i+1]-'0'<=5&&str2[i]-'0'<=6&&str2[i+1]-'0'>0&&str2[i]-'0'>0){
	ans+=str[str2[i+1]-'0'-1][str2[i]-'0'-1];
	}
	else{
	  ans="NA";
	  break;
	}
      }
      cout<<ans<<endl;
    }
  }
  return 0;
}