#include<fstream.h>

int main ()
{
	ifstream f("fact.in");
	ofstream g("fact.out");
	int p,n;
	f>>p;
	n=1;
	int k=0;
	int div5=0, div2=0;
	while (k<p)
	{
		n++;
		int x;
		x=n;
		while(x%2==0)
		{
			x=x/2;
			div2++;
		}
		while(x%5==0)
		{
			x=x/5;
			div5++;
		}
		if(div2>div5)
			k=div5;
		else
			k=div2;
	}
	if (k==p)
		g<<n;
	else
		g<<-1;
	g.close ();
	return 0;
}