#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, r;
  int i;
  const char *a[7] = {
      "afkpuz", "bglqv.", "chmrw?", "dinsx!", "ejoty ",
  };
  while (cin >> s) {
    r = "";
    for (i = 0; i + 1 < s.size(); i += 2) {
      if (s[i] > '6' || s[i + 1] > '5') break;
      r += a[s[i + 1] - '1'][s[i] - '1'];
    }
    if (i != s.size())
      cout << "NA" << endl;
    else
      cout << r << endl;
  }
  return 0;
}
