（-1/2）+（-1/6）+（-1/12）+ --------+（-1/132） =-(1-1/2)-(1/2-1/3)-(1/3-1/4)-.-(1/11-1/12) =-1+1/2-1/2+1/3-1/3+1/4-.-1/11+1/12 =-1+1/12 =-11/12
