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 r421041 = x;
        double r421042 = 1.0;
        double r421043 = r421041 + r421042;
        double r421044 = sqrt(r421043);
        double r421045 = sqrt(r421041);
        double r421046 = r421044 - r421045;
        double r421047 = y;
        double r421048 = r421047 + r421042;
        double r421049 = sqrt(r421048);
        double r421050 = sqrt(r421047);
        double r421051 = r421049 - r421050;
        double r421052 = r421046 + r421051;
        double r421053 = z;
        double r421054 = r421053 + r421042;
        double r421055 = sqrt(r421054);
        double r421056 = sqrt(r421053);
        double r421057 = r421055 - r421056;
        double r421058 = r421052 + r421057;
        double r421059 = t;
        double r421060 = r421059 + r421042;
        double r421061 = sqrt(r421060);
        double r421062 = sqrt(r421059);
        double r421063 = r421061 - r421062;
        double r421064 = r421058 + r421063;
        return r421064;
}