No problem, we've got 3871 and 4220 to multiply
3871 × 4220 = 4220 × (3871)
+ 4220 × 1 what gives us 4220
+ 4220 × 70 yielding 295400
+ 4220 × 800 what gives us 3376000
+ 4220 × 3000 yielding 12660000

= 16335620
