Ta có: $\frac{2019}{1}+$ $\frac{2018}{2}+...+$ $\frac{1}{2019}=$ $\frac{2019}{1}+1+$ $\frac{2018}{2}+1+...+$ $\frac{1}{2019}+1-2019$
=$\frac{2020}{1}+$ $\frac{2020}{2}+...+$ $\frac{2020}{2019}-2019$
=$ 1+\frac{2020}{2}+...+$ $\frac{2020}{2019}$
=$ \frac{2020}{2020}+\frac{2020}{2}+...+$ $\frac{2020}{2019}$
=$2020(\frac{1}{2}+$ $\frac{1}{3}+...+$ $\frac{1}{2020})$
Vậy G=2020
