var p,n,x,nr:longint;
    f,g:text;
begin
  assign(f,'fact.in');
  reset(f);
  assign(g,'fact.out');
  rewrite(g);
  readln(f,p);
  if p=0 then writeln(g,'1')
  else
    if p=1 then writeln(g,'10')
  else
  begin
    x:=0;
    nr:=1;
    while nr<=p*5 do
    begin
      inc(x);
      nr:=nr*5;
    end;
  end;
  n:=p*5-((x-2)*5);
  writeln(g,n);
  close(f);
  close(g);
end.