#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  bool poss = true;
  for (long long i = 2; i < s.length(); i++) {
    long long num = s[i] - 'A';
    long long prev = s[i - 1] - 'A';
    long long p_prev = s[i - 2] - 'A';
    if (num != (prev + p_prev) % 26) {
      poss = false;
    }
  }
  if (poss) {
    cout << "YES" << endl;
  } else {
    cout << "NO" << endl;
  }
  return 0;
}
