C++ :

#include<bits/stdc++.h>
using namespace std;
int n,s;
int main()
{   
    cin>>n;
	int ans=n/5*2;
	if(n%5==4) ans+=2;
	else if(n%5==1 || n%5==2 || n%5==3) ans++;
	cout<<ans;
    return 0;
}