#include <bits/stdc++.h>
using namespace std;
string ans, s;
string table[] = {"afkpuz", "bglqv.", "chmrw?", "dinsx!", "ejoty "};
int main() {
  while (cin >> s) {
    bool f = 0;
    ans = "";
    if (s.size() % 2 != 0) {
      cout << "NA" << endl;
      continue;
    }
    if (s.size() == 0) cout << "NA" << endl;
    for (int i = 0; i < s.size(); i += 2) {
      if (s[i] > '6' || s[i] < '1' || s[i + 1] > '6' || s[i] < '1') {
        f = 1;
        break;
      }
      ans += table[s[i + 1] - '1'][s[i] - '1'];
    }
    if (f)
      cout << "NA" << endl;
    else
      cout << ans << endl;
    ans.clear();
  }
}
