#include<iostream>
#include<fstream>
using namespace std;
int main()
{
	int nr,p,n,aux,i;
	ifstream f("fact.in");
	ofstream g("fact.out");
	f>>p;
	n=0;
	for(i=1;i<=p;i++;n=n+5)
	{	nr=0;
		aux=n/5;
		while(aux%5==0)
		{	nr++;
			aux=aux/5;
		}
		i=i+nr;
	}
	if(i>p+1)
		n=-1;
	if(p==0)
		n=1;
	g<<n;
	f.close();
	g.close();
	return 0;
}