My 800 followers problem!

Algebra Level 5

$\begin{array}{c}(799(x-y)& +& 800(y-z)& + &801(z-x) & =0 \\ 638401(x-y) & + & 640000(y-z) & +& 641601(z-x) & =800 \end{array}$

If $x,y,z$ satisfy the above system of equations then find the value of $x-2y+z$ .