Given,
S=(x,y):2y−y2≤x2≤2y,x≥y,
Now plotting the diagram, we get

Now from above diagram, given region are,
2y−y2≤x2, x2≤2y and x≥y
Now the intersecting point of {x}^{2}+{y}^{2}-2y=0&x=y will be (1,1) and {x}^{2}=2y&x=y will be (2,2)
So, required area will be,
A=∫01(1+1−x2−2x2)+∫12(x−2x2)dx
⇒A=(x−2x1−x2−21⋅sin−1x−6x3)01+(2x2−6x3)12
⇒A=67−4π=n+1n+2−x−1π
So, on comparing we get, n=5