Let $D=\{z: \Im z>0 \text{ and } |\Re z|<\pi/2\}$ be a half strip. Let $L_1$ be the left boundary $L_1:=\{z:\Re z=-\pi/2\ \text{ and } \Im z>0 \}$ and $L_2=\{z:\Re z=\pi/2\text{ and } \Im z>0\}$, $L_3=\{z:|\Re z|<\pi/2\text{ and } \Im z=0\}$.
I want to find a harmonic function $v$ such that $v$ takes 1 on $L_1$, $3$ on $L_2$, and equals $5$ on $L_3$
Efforts:
I know real and imaginary part of analytic function is harmonic. But I am not able to use it to solve the problem.
I would be thankful if somebody can give a small hint so that I can solev the problem on my own.