读下列古诗答题。

                                                                                                同李十一^①醉忆元九^②
                                                                                                        [唐]白居易
                                                                                       花时同醉破春愁，醉折花枝作酒筹。
                                                                                       忽忆故人天际去，计程今日到梁州。
      【注释】①李十一：李杓直，诗人的朋友。②元九：中唐诗坛上与白居易齐名的元稹。