1/2+(1/3+2/3)+(1/4+2/4+3/4)+(1/5+2/5+3/5+4/5)+···+(1/100+2/100+···+99/100)
=1/2+1+3/2+2+5/2+……+99/2
=1/2(1+2+3+4+5+……99)
=2475