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 r491005 = x;
        double r491006 = 1.0;
        double r491007 = r491005 + r491006;
        double r491008 = sqrt(r491007);
        double r491009 = sqrt(r491005);
        double r491010 = r491008 - r491009;
        double r491011 = y;
        double r491012 = r491011 + r491006;
        double r491013 = sqrt(r491012);
        double r491014 = sqrt(r491011);
        double r491015 = r491013 - r491014;
        double r491016 = r491010 + r491015;
        double r491017 = z;
        double r491018 = r491017 + r491006;
        double r491019 = sqrt(r491018);
        double r491020 = sqrt(r491017);
        double r491021 = r491019 - r491020;
        double r491022 = r491016 + r491021;
        double r491023 = t;
        double r491024 = r491023 + r491006;
        double r491025 = sqrt(r491024);
        double r491026 = sqrt(r491023);
        double r491027 = r491025 - r491026;
        double r491028 = r491022 + r491027;
        return r491028;
}