|1/2-1|+|1/3-1/2|+…+|1/99-1/98|+|1/100-1/99|
=(1-1/2)+(1/2-1/3)+...+(1/98-1/99)+(1/99-1/100)
=1-1/100
=99/100
|a-b|=|b-a|