#include<stdio.h>
int i,n;
long long k;
int main ()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&n);
	for(i=5;i<=n;i+=5)
	{
		n--;
	}
	k=n*5;
	printf("%lld",k);
	return 0;
}