#include <bits/stdc++.h>
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) {
    if (in.length() % 2) {
      cout << "NA" << endl;
      continue;
    }
    for (int i = 0; i < in.length() - 1; i += 2) {
      cout << str[in[i + 1] - '0'][in[i] - '0' - 1];
    }
    cout << endl;
  }
  return 0;
}
