\thm
There is an~algorithm which decides in time $\O(n^{1/2}\cdot m)$ whether there exists
-a~permutation satisfying a~given restriction graph.
+a~permutation satisfying a~given restriction graph. The $n$ and~$m$ are the number
+of vertices and edges of the restriction graph.
\proof
It is sufficient to verify that there exists a~perfect matching in the