#include <bits/stdc++.h>
using namespace std;
int main() {
  string str[6] = {"", "aafkpuz", "abglqv.", "achmrw?", "adinsx!", "aejoty "};
  string str2;
  while (cin >> str2) {
    if (str2.size() % 2 == 1)
      cout << "NA" << endl;
    else {
      string ans = "";
      for (int i = 0; i < str2.size(); i += 2) {
        if (str2[i + 1] - '0' <= 5 && str2[i] - '0' <= 6 &&
            str2[i + 1] - '0' > 0 && str2[i] - '0' > 0) {
          ans += str[str2[i + 1] - '0'][str2[i] - '0'];
        } else {
          ans = "NA";
        }
      }
      cout << ans << endl;
    }
  }
  return 0;
}
