133 Given two sets
$$
\begin{array}{c}
M=\left\{(x, y) \mid x^{2}+2 x+y^{2} \leqslant 0\right\}, \\
N=\{(x, y) \mid y \geqslant x+a\} .
\end{array}
$$

For $M \cap N=M$, the range of values for $a$ is $\qquad$ .
$133 a \leqslant 1-\sqrt{2}$.
$$
M \cap N=M \text { means } N \supseteq M .
$$
$M$ is a circle with center at $E(-1,0)$ and radius 1. The line $y=$ $x+a$ is below the circle. When the line is tangent to the circle, as shown in Figure 12, it is easy to know that $E A$ $=1 \div \cos 45^{\circ}=\sqrt{2}$. Therefore, point $A$ is $(\sqrt{2}-1,0)$, and from $0 \geqslant$ $\sqrt{2}-1+a$ we get $a \leqslant 1-\sqrt{2}$.