#include<bits/stdc++.h>//大佬帮帮我吧Q~Q
using namespace std;
int n,s,ans,p,mn=114514,bo;
int main(){
	cin>>n;
	if(n==4||n<=2) {cout<<-1;return 0;}
	if(n%5==0) {cout<<n/5;return 0;} 
	s=n; 
	while(s>0){
		if(s%3==0) {
			ans=p+s/3;
			if(ans<mn) mn=ans,bo=1;
		}
		s-=5;ans=0;p++;
	}
	if(bo==0) cout<<"-1";
	else cout<<mn;
	return 0;
}