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 r27405 = x;
        double r27406 = 1.0;
        double r27407 = r27405 + r27406;
        double r27408 = sqrt(r27407);
        double r27409 = sqrt(r27405);
        double r27410 = r27408 - r27409;
        double r27411 = y;
        double r27412 = r27411 + r27406;
        double r27413 = sqrt(r27412);
        double r27414 = sqrt(r27411);
        double r27415 = r27413 - r27414;
        double r27416 = r27410 + r27415;
        double r27417 = z;
        double r27418 = r27417 + r27406;
        double r27419 = sqrt(r27418);
        double r27420 = sqrt(r27417);
        double r27421 = r27419 - r27420;
        double r27422 = r27416 + r27421;
        double r27423 = t;
        double r27424 = r27423 + r27406;
        double r27425 = sqrt(r27424);
        double r27426 = sqrt(r27423);
        double r27427 = r27425 - r27426;
        double r27428 = r27422 + r27427;
        return r27428;
}