Cannot sample enough valid points. (more)

\[\left(\left(\left(\sqrt{x + 1} - \sqrt{x}\right) + \left(\sqrt{y + 1} - \sqrt{y}\right)\right) + \left(\sqrt{z + 1} - \sqrt{z}\right)\right) + \left(\sqrt{t + 1} - \sqrt{t}\right)\]
\left(\left(\left(\sqrt{x + 1} - \sqrt{x}\right) + \left(\sqrt{y + 1} - \sqrt{y}\right)\right) + \left(\sqrt{z + 1} - \sqrt{z}\right)\right) + \left(\sqrt{t + 1} - \sqrt{t}\right)
double f(double x, double y, double z, double t) {
        double r422867 = x;
        double r422868 = 1.0;
        double r422869 = r422867 + r422868;
        double r422870 = sqrt(r422869);
        double r422871 = sqrt(r422867);
        double r422872 = r422870 - r422871;
        double r422873 = y;
        double r422874 = r422873 + r422868;
        double r422875 = sqrt(r422874);
        double r422876 = sqrt(r422873);
        double r422877 = r422875 - r422876;
        double r422878 = r422872 + r422877;
        double r422879 = z;
        double r422880 = r422879 + r422868;
        double r422881 = sqrt(r422880);
        double r422882 = sqrt(r422879);
        double r422883 = r422881 - r422882;
        double r422884 = r422878 + r422883;
        double r422885 = t;
        double r422886 = r422885 + r422868;
        double r422887 = sqrt(r422886);
        double r422888 = sqrt(r422885);
        double r422889 = r422887 - r422888;
        double r422890 = r422884 + r422889;
        return r422890;
}