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