#include <bits/stdc++.h>
const char symbol[4] = {'.', '?', '!', ' '};
int main() {
  std::string s;
  while (std::cin >> s) {
    if (s.size() & 1)
      std::cout << "NA" << std::endl;
    else {
      std::string res;
      bool f = true;
      for (int i = 0; i < s.size(); i += 2) {
        if (s[i] < '0' || s[i] > '6' || s[i + 1] < '0' || s[i + 1] > '5') {
          f = false;
          break;
        }
        int n = (s[i] - '1') * 5 + s[i + 1] - '1';
        if (n > 29) {
          f = false;
          break;
        } else
          res += n >= 26 ? symbol[n - 26] : 'a' + n;
      }
      std::cout << (f ? res : "NA") << std::endl;
    }
  }
  return 0;
}
