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