#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(!cin.tie(0));
  string s;
  cin >> s;
  vector<int> a;
  for (char c : s) {
    a.push_back(c - 'A');
  }
  for (int i = 2; i < (int)s.size(); i++) {
    if ((a[i - 2] + a[i - 1] - a[i]) % 26) {
      cout << "NO\n";
      return 0;
    }
  }
  cout << "YES\n";
}
