Za nNn \in \mathbb{N} definiramo kompleksan broj

an=(1+i)(1+i2)(1+i3)(1+in).a_n = (1 + i) \left(1 + \frac{i}{\sqrt{2}}\right) \left(1 + \frac{i}{\sqrt{3}}\right) \cdots \left(1 + \frac{i}{\sqrt{n}}\right).

Izračunaj

a1a2+a2a3++a2019a2020.\left| a_1 - a_2 \right| + \left| a_2 - a_3 \right| + \cdots + \left| a_{2019} - a_{2020} \right|.