#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  string s;
  cin >> s;
  int n = s.length();
  vector<int> a(n);
  for (int i = 0; i < n; i++) {
    a[i] = s[i] - 'A';
  }
  bool is = true;
  for (int i = 2; i < n; i++) {
    if (a[i] != (a[i - 1] + a[i - 2]) % 26) {
      is = false;
    }
  }
  if (is) {
    cout << "YES"
         << "\n";
  } else
    cout << "NO\n";
  cerr << "time taken : " << (float)clock() / CLOCKS_PER_SEC << " secs"
       << "\n";
  return 0;
}
