取重心:
(1+2*2+3*3+100*100)/(1+2+...+100)
=(100*101*201/6 ) / (100*101/2)
=201/3
=67
∴ x=67时,值最小
=66+2*65+3*64+...+66*1+67*0+68*1+...+99*32+100*33