No problem, we've got 9960 and 8640 to multiply
9960 × 8640 = 8640 × (9960)
+ 8640 × 0 what gives us 0
+ 8640 × 60 resulting in 518400
+ 8640 × 900 what gives us 7776000
+ 8640 × 9000 that is equal 77760000

= 86054400
