$\text{A = 1.2.3.....2018 - 1.2.3.....2017 - 1.2.3.....2016.$2017^{2}$ }$
$\text{ = 1.2.3.....2018 - 1.2.3.....2017.1 - 1.2.3.....2016.2017.2017 }$
$\text{ = 1.2.3.....2018 - 1.2.3.....2016.2017.(2017 + 1) }$
$\text{ = 1.2.3.....2018 - 1.2.3.....2018 }$
$\text{ = 0}$
$\text{CHÚC BẠN HỌC TỐT!}$