\Phi\left(\mathbf{x}\right)=\int\limits_{0}^{\frac{\pi}{2}}\left(x'_1^2\left(t\right)+x'_2^2\left(t\right)+x'_3^2\left(t\right)-x_1^2\left(t\right)-x_2^2\left(t\right)-2x_3\left(t\right)\right)dt,