#include <fstream>
using namespace std;
int main ()
{	int N=0,p,i;
	ifstream fcin("fact.in");
	ofstream fcout("fact.out");
	fcin>>p;
	if(p==0)fcout<<1;
	else
	{	for(i=1;i<=p;i++)
	{	if (i%5==0)
			i=i+i/5;
		N=N+5;
	}
	fcout<<N;}
	fcin.close();
	fcout.close();
	return 0;
}