For x ∈ R, two real valued functions f(x) and g(x) are such that, g(x)=√ x +1 and f ° g(x)=x+3-√ x. Then f(0) is equal to

For $\displaystyle x \in \mathbb{R}$, two real valued functions $\displaystyle f(x)$ and $\displaystyle g(x)$ are such that, $\displaystyle g(x)=\sqrt{x}+1$ and $\displaystyle f \circ g(x)=x+3-\sqrt{x}$. Then $\displaystyle f(0)$ is equal to