#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, t = "ceeeksy";
  cin >> s;
  sort(s.begin(), s.end());
  int pointer = 0;
  for (int i = 0; i < s.size(); i++) {
    if (t[pointer] == s[i]) pointer++;
    if (pointer == t.size()) break;
  }
  if (pointer == t.size())
    cout << "YES";
  else
    cout << "NO";
}
