#include <bits/stdc++.h>
using namespace std;
int main(){
  string s; cin >> s;
  int cntx = 0;
  for(int i = 0; i < s.length(); i++)if(s[i]=='x')cntx++;
  cout << (((15 - cntx)>=8) ? "YES" : "NO") << endl;
  return 0;
}