#include<iostream>
#include<string>

using namespace std;

string str[6];

void make(){
  str[1] = "afkpuz";
  str[2] = "bglqv.";
  str[3] = "chmrw?";
  str[4] = "dinsx!";
  str[5] = "ejoty ";
}
int main(){
  make();
  string in;
  while(cin >> in){
    string out;
    if(in.length()%2){
      cout << "NA" << endl;
      continue;
    }
    int status = 0;
    for(int i = 0; i < in.length(); i++){
      if(in[i] < '1' || in[i] > '7') status = 1;
    }
    if(status){
      cout << "NA" << endl;
      continue;
    }
    for(int i = 0; i < in.length()-1; i+=2){
      if(in[i+1]-'0' >= 6){
	status = 1;
	break;
      }
      out += str[in[i+1]-'0'][in[i]-'0'-1];
    }
    if(status) cout <<"NA" <<endl;
    else cout << out << endl;
  }
  return 0;
}