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 r761881 = x;
        double r761882 = 1.0;
        double r761883 = r761881 + r761882;
        double r761884 = sqrt(r761883);
        double r761885 = sqrt(r761881);
        double r761886 = r761884 - r761885;
        double r761887 = y;
        double r761888 = r761887 + r761882;
        double r761889 = sqrt(r761888);
        double r761890 = sqrt(r761887);
        double r761891 = r761889 - r761890;
        double r761892 = r761886 + r761891;
        double r761893 = z;
        double r761894 = r761893 + r761882;
        double r761895 = sqrt(r761894);
        double r761896 = sqrt(r761893);
        double r761897 = r761895 - r761896;
        double r761898 = r761892 + r761897;
        double r761899 = t;
        double r761900 = r761899 + r761882;
        double r761901 = sqrt(r761900);
        double r761902 = sqrt(r761899);
        double r761903 = r761901 - r761902;
        double r761904 = r761898 + r761903;
        return r761904;
}