The function \( f(x, y) \) satisfies the Laplace equation
\[
\nabla^2 f(x, y) = 0
\]
on a circular domain of radius \( r = 1 \) with its center at point P with coordinates \( x = 0, y = 0 \). The value of this function on the circular boundary of this domain is equal to 3.
The numerical value of \( f(0, 0) \) is: