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 r515767 = x;
        double r515768 = 1.0;
        double r515769 = r515767 + r515768;
        double r515770 = sqrt(r515769);
        double r515771 = sqrt(r515767);
        double r515772 = r515770 - r515771;
        double r515773 = y;
        double r515774 = r515773 + r515768;
        double r515775 = sqrt(r515774);
        double r515776 = sqrt(r515773);
        double r515777 = r515775 - r515776;
        double r515778 = r515772 + r515777;
        double r515779 = z;
        double r515780 = r515779 + r515768;
        double r515781 = sqrt(r515780);
        double r515782 = sqrt(r515779);
        double r515783 = r515781 - r515782;
        double r515784 = r515778 + r515783;
        double r515785 = t;
        double r515786 = r515785 + r515768;
        double r515787 = sqrt(r515786);
        double r515788 = sqrt(r515785);
        double r515789 = r515787 - r515788;
        double r515790 = r515784 + r515789;
        return r515790;
}