#include <bits/stdc++.h>
using namespace std;
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) {
      ans += str[str2[i + 1] - '0' - 1][str2[i] - '0' - 1];
    }
    cout << ans << endl;
  }
  return 0;
}
