var pu,p:longint;
		f:text;
procedure func(nr:longint);
var n,r,i:longint;
begin
  r:=0;
  pu:=5;
	while nr div pu>0 do
   	begin
     	inc(r,nr div pu);
      pu := pu * 5;
    end;
  if r > p then
  	func(nr-5)
  else if r = p then
  	write(f,nr);
end;
begin
  assign(f,'fact.in');reset(f);
	read(f,p);
  assign(f,'fact.out');rewrite(f);
  if p=0 then
  	write(f,1)
  else
	  func(p*5);
  close(f);
end.