#include <bits/stdc++.h>

using namespace std;

int main() {
  string S;
  cin >> S;
  int cnt = 0;
  for (int i = 0; i < (int)S.size(); ++i) {
    if (S[i] == 'x') cnt++;
  }
  cout << (cnt <= 7 ? "YES": "NO") << endl;
  return 0;
}

