program infoarena_factorial;
uses math;
 var p,n,y:int64;
   f:text;
begin
  assign(f,'fact.in');reset(f);readln(f,p);close(f);
  assign(f,'fact.out');rewrite(f);
  if p=0 then begin n:=1;write(f,n);close(f);end
  else begin
  n:=0;y:=0;
  while p>0 do
begin
  n:=n+5; p:=p-1;
  if ((n div 5) mod 5)=0 then begin y:=y+1;p:=p-y;end;
end;   write(f,n);close(f);
  end;
end.