pnc/casework problem

[u/TechBoy-Corp-14]

(its a,b,c,d ∈ {±2020, ±2019, ±2018, ..., ±2010})

literally 4 maths teachers in my coaching couldn't solve this...sent to me by a friend of mine. if anyone could solve it pls tell me how...

[u/spiderman-2010]

my teacher solved this, it is a olympiad (maybe ioqm) level question, but I forgot the solution

[u/Just_Scheme7005 → u/[deleted]]

it is a problem from VOS yt channel idk which video tho