Let $$\mathbb{R}$$ denote the set of all real numbers. Let $$a_i, b_i \in \mathbb{R}$$ for $$i \in \{1, 2, 3\}$$. Define the functions $$f: \mathbb{R} \to \mathbb{R}$$, $$g: \mathbb{R} \to \mathbb{R}$$, and $$h: \mathbb{R} \to \mathbb{R}$$ by
$$f(x) = a_1 + 10x + a_2 x^2 + a_3 x^3 + x^4,$$
$$g(x) = b_1 + 3x + b_2 x^2 + b_3 x^3 + x^4,$$
$$h(x) = f(x+1) - g(x+2).$$
If $$f(x) \neq g(x)$$ for every $$x \in \mathbb{R}$$, then the coefficient of $$x^3$$ in $$h(x)$$ is
















