#include<fstream.h>
ifstream f("fact.in");
ofstream g("fact.out");
long p,li,ls,m,y,nr,z;
int main ()
{
f>>p;
li=1;
ls=1000000000;
if(p==0)
  g<<"1"<<"\n";
  else
{while(li<=ls)
    {m=(ls+li)/2;
    y=m;
    nr=0;
    z=5;
    while(z<=y)
	 {nr=nr+y/z;
	 z=z*5;}
    if(nr==p)
      break;
      else
      if(nr>p)
	ls=m-1;
	else
	li=m+1;}
	if(li>ls)
	   g<<"-1"<<"\n";
	   else
	   {while(m%5!=0)
		  m--;
	     g<<m;}}
f.close();
g.close();
return 0;
}