#include<bits/stdc++.h>
using namespace std;
int main(){
	string s;
	cin>>s;
	int ans=0;
	for(int i=0;i<s.length();i++)
		if(s[i]=='x') ans++;
	if(ans>7) cout<<"NO\n";
	else cout<<"YES\n";
	return 0;
}