“上升索引 i(i>1)i(i > 1)i(i>1),即 ui>ui−1u_i>u_i-1ui>ui−1” 应该为 “上升索引 i(i>1)i(i > 1)i(i>1),即 ui>ui−1u_i>u_{i-1}ui>ui−1”。