#include <bits/stdc++.h>
using namespace std;
int main() {
  string po[6] = {{" "},
                  {' ', 'a', 'f', 'k', 'p', 'u', 'z'},
                  {' ', 'b', 'g', 'l', 'q', 'v', '.'},
                  {' ', 'c', 'h', 'm', 'r', 'w', '?'},
                  {' ', 'd', 'i', 'n', 's', 'x', '!'},
                  {' ', 'e', 'j', 'o', 't', 'y', ' '}};
  string s;
  while (cin >> s) {
    if (s.size() % 2 == 1) {
      cout << "NA" << endl;
    } else {
      for (int i = 0; i < s.size(); i += 2) {
        string x, y;
        x = s[i + 1];
        y = s[i];
        cout << po[stoi(x)][stoi(y)];
      }
      cout << endl;
    }
  }
}
