#include <fstream.h>
int main ()
{int i,m,s=0;
long p,x=0;
ifstream f("fact.in");
ofstream g("fact.out");
f>>p;
if(p==0) g<<-1;
else
for (i=0;i<=p*5;i=i+5)
	{m=i;
	while (m%5==0)
		{if(m==0) break;
		m=m/5;
		s=s+1;
		if (m==1) break;
		}
	if (m!=0) x=x+1;
	if (s==p) {g<<x*5; break;}
	else if (s>p) {g<<-1; break;}
	}
return 0;
}