#include <iostream>
using namespace std;

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){
      ans += str[str2[i+1] - '0'-1][str2[i] - '0'-1]; 
    }
    cout << ans << endl;
  }
  return 0;
}