Pa求助，为什么我只有70分

var s:string;
    i,j,k:integer;
begin
  readln(s);
  k:=length(s);
  if (s[1]='-') then write('-');
  for i:=k downto 1 do begin
    if (s[i]>='1') and (s[i]<='9') then write(s[i]);
  end;
end.