#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long LL;
const int INF=0x3f3f3f3f;
LL n,sum,Plus;
bool flag[10];
int MaxDep;
bool dfs(int x,int dep)
{
	if (dep>MaxDep) return 0;
	if (x==0) return 1;
	bool find=0;
	for (int i=1;i<=5;++i)
		if (n-x>=5-i&&x>=i) find=find||dfs(x-i+5-i,dep+1);
	return find;
}
LL ans;
int main()
{
freopen("xcoin.in","r",stdin);
freopen("xcoin.out","w",stdout);
	scanf("%lld",&n);
	ans=0;
	if (n>30) 
	{
		ans=(n-20)/5;
		n=(n-20)%5+20;
	}
	{	
		MaxDep=-1;
		for (;;)
		{
			++MaxDep;
			if (dfs(n,0)) break;
		}
		printf("%lld\n",ans+MaxDep);
	}
	return 0;
}