#include <fstream>
using namespace std;
ifstream f1 ("fact.in");
ofstream f2 ("fact.out");
int main()   
{   
long n,p,r,m;
f1>>p;
f1.close();
r=p;
n=0;
while (r>0)
  {n=n+5;
   m=n/5;
   if (m%5==0) m=m/5;
   if (m%5==0) m=m/5;
   if (m%5==0) m=m/5;
   if (m%5==0) m=m/5;
   if (m%5==0) m=m/5;
   if (m%5==0) m=m/5;
   if (m%5==0) m=m/5;
   r=r-m;}
if (p!=0) 
  {if (r==0) f2<<n;   
      else f2<<"-1";}   
 else f2<<"1"; f2.close();   
}