#include <iostream>
using namespace std;
const string str[] = {"abkpuz",
		      "bglqv.",
		      "chmrw?",
		      "dinsx!",
		      "ejoty "};
int main(){
  string str2;
  while( cin >> str2 ){ 
    string ans="";
    if(str2.size()%2 == 1){
      cout << "NA" << endl;
      continue;
    }
    for(int i = 0 ; i < (int)str2.size() ; i+=2){
      if(!(0 <= str2[i+1]-'0'-1 && str2[i+1]-'0'-1 < 5 &&
	 0 <= str2[i]-'0'-1 && str2[i]-'0'-1 < 6)){
	cout << "NA" << endl;
	goto N;
      }
      ans += str[(str2[i+1] - '0')-1][(str2[i] - '0')-1]; 
    }
    cout << ans << endl;
  N:;
  }
  return 0;
}