#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
int main(){
    int n=0;
    string s;
    cin>>s;
    rep(i,s.size()) if(s[i]=='x') n++;
    if(15-n>=8) cout<<"YES";
    else cout<<"NO";
}