#include<iostream.h>
#include<fstream.h>
#include<math.h>
fstream f("fact.in",ios::in), g("fact.out",ios::out);
long long contor,i,ok,ur=1,p,b;
int main()
{
	long long k,v,pu=5,l;
	f>>k;
	while(contor<k && !ok)
	{
		i+=pu;
		contor+=ur;
		if(i==pu*5)
		{	contor++;
			ur=contor;
			pu=pu*5;
			
		}
		if(contor>k)
			ok=1;
	}
	p=pu/5;
	l=ur;v=pu;b=(ur-1)/5;
	while(ok && v<i)
	{
		v+=p;
		l+=b;
		if(l>k)
		{	l-=b;v-=p;b=(b-1)/5;p=p/5;}
		if(l==k)
			ok=0;
	}
	if(ok==1)
	{	g<<"-1";cout<<"-1";}
	else
	{	g<<v;cout<<v;}
	return 0;
}