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