#include<fstream>
//#include<iostream>

using namespace std;

int main()
{
	long long sol, p, i=0, n=0, k=0, ver;
	ifstream f ("fact.in");
	ofstream g ("fact.out");
	f>>p;
	
	for (i=1;i<=p;i++)
	{
		n=n+5;
		ver = -1;
		k=n;
		while(k%5==0 && k>0)
		{
			ver++;
			k=k/5;
		}
		i = i+ver;
		//cout<<i<<" "<<n<<"\n";
	}
	i--;
	
	if (p==0)
		g<<1;
	else
		if (i>p)
			g<<-1;
		else
			g<<n;
	f.close();
	g.close();
	
	return 0;
}