#include <bits/stdc++.h>
using namespace std;
int main() {
  char a[7][7] = {"",       "*abcde", "*fghij", "*klmno",
                  "*pqrst", "*uvwxy", "*z.?! "};
  string s;
  while (cin >> s) {
    if (s.size() % 2 == 1)
      cout << "NA" << endl;
    else {
      for (int i = 0; i < s.size(); i += 2) {
        cout << a[s[i] - 48][s[i + 1] - 48];
      }
      cout << endl;
    }
  }
  return 0;
}
