#include <bits/stdc++.h>
using namespace std;
int main() {
  string word;
  cin >> word;
  if (word.length() <= 2) {
    cout << "YES" << endl;
    return 0;
  }
  for (int i = 2; i < word.length(); i++) {
    if ((word[i - 1] + word[i - 2] - 'A' - 'A') % 26 != (word[i] - 'A')) {
      cout << "NO" << endl;
      return 0;
    }
  }
  cout << "YES" << endl;
  return 0;
}
