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