????? ????????L L/2 L/2 LL ab L q L/2 L/2 L q aL q c ???? ??? ????? ???L aacL abL ab L=n*c c/cc c/2 L=n*ccc ???????? ???? ????? L=n*c c/cc c/2 qL qaaLqacaLqL dab c ????? ???????? ??L qL dab cL bacac bq L/2 L/2 L qL abL q ??????? ??????LabLL ab aaL L L/2 L/2 L ??? ??????? ???? aaLL q L q L qdcabL q ???????? ?????LL L/2 L/2 L qL L/2 L/2 qL abaaL ???? ????????L abqL L=n*c c/cc c/2 L=n*c aaL q ??? ???? ????? ?? aaL qL aca qcdbaL qL q L L/2 L/2 q
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