#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;
if (p>0)
 {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;
    r=r-m;}
  if (r==0) f2<<r;
   else f2<<=1;}
 else n=1;
 f2<<n;}