#include <bits/stdc++.h>
using namespace std;

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