# Wanna do this 29 years before now?

Calculus Level 4

$\prod _{ n=2 }^{ 1986 } \Bigg({ 1-\frac { 1 }{\displaystyle \sum _{ k=0 }^{ n }{ k } } } \Bigg)$

If the product above equals to $$\frac a b$$ for some relatively coprime positive integers $$a,b$$, find $$b-a$$.

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