Gram-Schmidt orthogonalization: finding an orthogonal set

Question

Does anyone know how to solve this problem?

Let $f_{1}(x)=x, f_{2}(x)=x^{2}, f_{3}(x)=x^{3} \in L^{2}[0,1]$ , Find an orthonormal set from $\left\{f_{1}(x), f_{2}(x), f_{3}(x)\right\}$ by using the Gram-Schmidt orthogonalization.