#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j = -1;
  char c, d, s[201], r[1024][101],
      t[5][7] = {"afkpuz", "bglqv.", "chmrw?", "dinsx!", "ejoty "};
  bool f;
  while (cin >> s) {
    if (cin.eof()) break;
    j++;
    if (strlen(s) % 2 == 0) {
      for (i = f = 0; i < strlen(s); i += 2, f = 0) {
        c = s[i], d = s[i + 1];
        if (atoi(&c) > 6 || atoi(&d) > 5) {
          strcpy(r[j], "NA");
          f = 1;
          break;
        }
        r[j][i / 2] = t[atoi(&d) - 1][atoi(&c) - 1];
      }
      if (f) continue;
      r[j][i / 2] = '\0';
    } else
      strcpy(r[j], "NA");
  }
  for (i = 0; i < j; i++) cout << r[i] << endl;
}
