1+2-3+4+5-6+7+8-9+……+97+98-99 +100 =(1+2-3)+(4+5-6)+(7+8-9)+……+(97+98-99) +100 =0+3+6+.+96+100 =1*3+2*3+.+32*3+100 =3*(1+2+3+...+32)+100 =3*(1+32)*32/2+100 =3*33*16+100 =1584+100 =1684