#include <bits/stdc++.h>
using namespace std;
char M[6][6] = {"abcde", "fghij", "klmno", "pqrst", "uvwxy", "z.?! "};
string s;
int main() {
  while (cin >> s) {
    if (s.size() % 2) {
      cout << "NA" << endl;
      continue;
    }
    bool f = 1;
    for (int i = 1; i < s.size(); i += 2)
      if (s[i] > '5') f = 0;
    if (!f) {
      cout << "NA" << endl;
      continue;
    }
    for (int i = 0; i < s.size(); i += 2) {
      cout << M[s[i] - '1'][s[i + 1] - '1'];
    }
    cout << endl;
  }
}
