#include <bits/stdc++.h>
using namespace std;
const string characters = "abcdefghijklmnopqrstuvwxyz.?! ";
string convert(const string &number) {
  if (number.size() & 1) return "NA";
  string res = "";
  for (unsigned i = 0; i < number.size(); i += 2) {
    if (!('1' <= number[i] && number[i] <= '6')) return "NA";
    if (!('1' <= number[i] && number[i] <= '5')) return "NA";
    const unsigned idx = (number[i] - '1') * 5 + (number[i + 1] - '1');
    if (idx >= characters.size()) return "NA";
    res += characters[idx];
  }
  return res;
}
int main() {
  string number;
  while (cin >> number) {
    cout << convert(number) << endl;
  }
  return EXIT_SUCCESS;
}
