123456789*987654321-123456788*987654322=(123456788+1)*987654321-123456788*(987654321+1)
=987654321-123456788
=864197533
123456789*987654321-123456788*987654322
=123456789*987654321-(123456789-1)*(987654321+1)
=123456789*987654321-123456789*987654321 -123456789 +987654321
=987654321 - 123456789
=864197532
1