题目寻找下标答题地址：http//pkuic.openjudge.cn/ziyoulianxi//AfedddecafbbedbffabadcfefddBaafcfefbbaebaadfccebfcCcecffebbcbcddeabedeabfebdfdbabcDdbfabcdaeebffcacdedbEbbcfcdeabbdcecaceaaaf