#include <bits/stdc++.h>
using namespace std;
char table[5][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', ' '}};
int main() {
  string s;
  while (cin >> s) {
    if (cin.eof()) break;
    if (s.size() % 2) {
      cout << "NA" << endl;
      continue;
    }
    for (int i = 0; i < s.size(); i += 2)
      cout << table[s[i + 1] - '0' - 1][s[i] - '0' - 1];
    cout << endl;
  }
}
