СAΪһѧңһA1,A2...An
ÿοԽ²ѡһi,(Ai-1,Ai,Ai+1)
Ϊ(Ai-1 + Ai,-Ai,Ai+1 + Ai),رأi=N,(An-1,An)Ϊ
(An-1 + An,-An).СAܺ棬ܷͨɴβõB1,B2...Bn.̫С㣬