1/2+1/5+1/8+1/11+1/20+1/41+1/110+1/1640=1,
则：-1/2-1/5-1/8+1/11-1/20-1/41+1/110+1/1640
=-1+2*[(1/11)+(1/110)+(1/1640)]
=-1+2*(165/1640)
=-131/164