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 r421558 = x;
        double r421559 = 1.0;
        double r421560 = r421558 + r421559;
        double r421561 = sqrt(r421560);
        double r421562 = sqrt(r421558);
        double r421563 = r421561 - r421562;
        double r421564 = y;
        double r421565 = r421564 + r421559;
        double r421566 = sqrt(r421565);
        double r421567 = sqrt(r421564);
        double r421568 = r421566 - r421567;
        double r421569 = r421563 + r421568;
        double r421570 = z;
        double r421571 = r421570 + r421559;
        double r421572 = sqrt(r421571);
        double r421573 = sqrt(r421570);
        double r421574 = r421572 - r421573;
        double r421575 = r421569 + r421574;
        double r421576 = t;
        double r421577 = r421576 + r421559;
        double r421578 = sqrt(r421577);
        double r421579 = sqrt(r421576);
        double r421580 = r421578 - r421579;
        double r421581 = r421575 + r421580;
        return r421581;
}