#include <bits/stdc++.h>
using namespace std;
char decode(int a, int b) {
  int x = a * 5 + b;
  if (x < 26) return x + 'a';
  return ".?! "[x - 26];
}
int main() {
  string s;
  while (cin >> s) {
    if (s.size() % 2) {
      cout << "NA\n";
      continue;
    }
    for (int i = 0; i < s.size(); i += 2) {
      cout << decode(s[i] - '1', s[i + 1] - '1');
    }
    cout << endl;
  }
  return 0;
}
