If a function
\[
f:[1,7]\rightarrow\mathbb{R}
\]
is defined as
\[
f(x)=
\begin{cases}
2x^2-1, & x\le\sqrt7,[2mm]
\sqrt{7x}+6, & \sqrt7[2mm]
\sin\pi x, & 5\le x\le6,[2mm]
x-[x], & 6<x\le7,
\end{cases}
\]
then the number of points of discontinuity in \([1,7]\) is