#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e9 + 7;
const long long MOD = 998244353;
const long long inf = INF * INF;
const long long mod = MOD;
const long long MAX = 2000010;
signed main() {
  string s;
  cin >> s;
  long long n = s.size();
  bool f = 1;
  for (int i = (2); i < (n); i++) {
    if (((s[i - 1] - 'A') + (s[i - 2] - 'A')) % 26 != s[i] - 'A') f = 0;
  }
  cout << (f ? "YES" : "NO") << '\n';
}
