Let
\[
B = \{(x,y,z) \in \mathbb{R}^3 : x^2 + y^2 + z^2 \le 1 \}
\]
and define
\[
u(x,y,z) = \sin\!\left(\pi(1 - x^2 - y^2 - z^2)^2\right)
\]
for \((x,y,z) \in B.\)
Then the value of
\[
\iiint_B \left(
\frac{\partial^2 u}{\partial x^2} +
\frac{\partial^2 u}{\partial y^2} +
\frac{\partial^2 u}{\partial z^2}
\right) \, dx\,dy\,dz
\]
is _________.