#include<fstream.h>
 ifstream f("fact.in");
 ofstream g("fact.out");
 long n,p,m,nr,z,li,ls,y;
 int main()
 {f>>p;
 if(p==0)
	g<<0<<'\n';
 li=1;
 ls=100000000;
 while(li<=ls)
	  {m=(li+ls)/2;
	   nr=0;
	   z=5;
	   y=m;
	   while(z<=y)
			 {nr=nr+y/z;
			 z=z*5;
			 }
	 if(nr==p)
	 break;
	 else
	 if(m>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;
   }