\(\left|x-1\right|+\left|x-2\right|+...+\left|x-2019\right|=\)
\(\left|x-1\right|+\left|2-x\right|+\left|x-3\right|+\left|4-x\right|+....+\left|x-2017\right|+\left|2018-x\right|+\left|x-2019\right|\)
\(\ge\)
\(\left|x-1+2-x+x-3+4-x+....+x-2017+2018-x+x-2019\right|\)
= \(\left|-1+2-3+4-...-2017+2018-2019\right|=2019\)
\(\)