999 x 998998999 - 998 x 999999998 =999 x (999999999-1001000) - (999-1) x (999999999-1 ) =999 x 999999999-999999000-999 x 999999999+999+999999999-1 =2x999-1 =2000-3 =1997
999 x 998998999 - 998 x 999999998 =999x(998000000+998000+999)-998x(999000000+999000+998) =999x998000000+999x998000+999x999-998x999000000-998x999000-998x998 999x998000000=999x998x1000000=9...