#include <bits/stdc++.h>
using namespace std;
const string str[] = {"abkpuz", "bglqv.", "chmrw?", "dinsx!", "ejoty "};
int main() {
  string str2;
  while (cin >> str2) {
    string ans = "";
    if (str2.size() % 2 == 1) {
      cout << "NA" << endl;
      continue;
    }
    for (int i = 0; i < (int)str2.size(); i += 2) {
      if (!(0 <= str2[i + 1] - '0' - 1 && str2[i + 1] - '0' - 1 < 5 &&
            0 <= str2[i] - '0' - 1 && str2[i] - '0' - 1 < 6)) {
        cout << "NA" << endl;
        goto N;
      }
      ans += str[(str2[i + 1] - '0') - 1][(str2[i] - '0') - 1];
    }
    cout << ans << endl;
  N:;
  }
  return 0;
}
