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 r1521 = x;
        double r1522 = 1.0;
        double r1523 = r1521 + r1522;
        double r1524 = sqrt(r1523);
        double r1525 = sqrt(r1521);
        double r1526 = r1524 - r1525;
        double r1527 = y;
        double r1528 = r1527 + r1522;
        double r1529 = sqrt(r1528);
        double r1530 = sqrt(r1527);
        double r1531 = r1529 - r1530;
        double r1532 = r1526 + r1531;
        double r1533 = z;
        double r1534 = r1533 + r1522;
        double r1535 = sqrt(r1534);
        double r1536 = sqrt(r1533);
        double r1537 = r1535 - r1536;
        double r1538 = r1532 + r1537;
        double r1539 = t;
        double r1540 = r1539 + r1522;
        double r1541 = sqrt(r1540);
        double r1542 = sqrt(r1539);
        double r1543 = r1541 - r1542;
        double r1544 = r1538 + r1543;
        return r1544;
}