# Constraints On Cylinders And Planes

Algebra Level 3

$$x,y,$$ and $$z$$ are real numbers satisfying $$x^2+y^2 =1$$ and $$y+z=1$$.

Let $$M$$ and $$m$$ be the maximum and minimum values of the expression $$x+2y+z$$, respectively.

Find $$M+m$$.