P(x,y)
y^2=2x
d=√[(x-m)^2+y^2]=√[(x-m)^2+2x]
x^2+(2-2m)x+m^2-d^2=0
(2-2m)^2-4(m^2-d^2) ≥0
d^2 ≥2m-1
3=2m-1
m=2