999.99×999.99＋1999.99
=(1999...99-1000...00)×999...99+1999...99
=1999...99×999...99-1000...00×999...99
+1999...99
=1999...99×(999...99+1)-1000...00×999...99
=1999...99×1000...00-1000...00×999...99
=1000...00×(1999...99-999...99)
=1000...00×1000...00
=1000.00(共1992*2=3984个零)