When z=1, we have
1=h/2 +1
Subtracting 1 from both sides we get
0=h/2
Solving for h we get h=0
So when h=0, z=1
Similarly when z=2, we get
2=h/2 +1
Subtracting 1 from both sides we get
h/2=1
Multiplying both sides by 2 we get
h=2
So when h=2, z=2
Similarly when z=3, we get
3=h/2 +1
Subtracting 1 from both sides we get
2=h/2
Multiplying both sides by 2 we get h=4
So when z=3, h=4
Lastly, when z=4, we have
4=h/2 +1
Subtracting 1 from both sides we get
3=h/2
Multiplying both sides by 2 we get
h=6
So when z=4, h=6
Hope this helps!