#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");

int p,l,r;

int cautare()
{
	if (p==0) return 1;
	while (l<=r)
	{
		int m;
		in mij=(l+r)/2;
		n=0;
		m=mij;
		while (m!=0)
		{
			n += m/5;
			m /= 5;
		}
		if (n==p)
		{
			return mij-mij%5;
		}
		if (n<p)
			l=mij+1;
		else r=mij-1;
	}
	return -1;
}

int main()
{
	f>>p;
	l=0;
	r=2000000000;
	g<<cautare();
	f.close();
	g.close();
	return 0;
}