My heart gave a leap when I heard the announcement that our train would soon arrive at its destination-Beijing. Like other passengers, I began to collect my things and put my mug,towel,atlas,apples,and other things into my bag. To the tune of a beautiful song the train pulled into the station and gently stopped by a platform.I walked out of the train and was carried forward by the stream of people into an underground passage and then into a big hall.As I stepped out of the station,I was dazzled by the bright autumn skies of Beijing. Though I had been on the train for more than thirty hours and spent a sleepless night, I didn't feel tired at all,and I believe my days in Beijing would be as sunny as the skies. The organizational pattern of this passage is ______.