|Codeforces Round #227 (Div. 2)|
George loves graphs. Most of all, he loves interesting graphs. We will assume that a directed graph is interesting, if it meets the following criteria:
However, not everything's that simple. George got a directed graph of n vertices and m arcs as a present. The graph didn't have any multiple arcs. As George loves interesting graphs, he wants to slightly alter the presented graph and transform it into an interesting one. In one alteration he can either remove an arbitrary existing arc from the graph or add an arbitrary arc to the graph.
George wonders: what is the minimum number of changes that he needs to obtain an interesting graph from the graph he's got as a present? Help George and find the answer to the question.
The first line contains two space-separated integers n and m (2 ≤ n ≤ 500, 1 ≤ m ≤ 1000) — the number of vertices and arcs in the presented graph.
Each of the next m lines contains two space-separated integers a i, b i (1 ≤ a i, b i ≤ n) — the descriptions of the graph's arcs. Pair (a i, b i) means that the graph contains an arc from vertex number a i to vertex number b i. It is guaranteed that the presented graph doesn't contain multiple arcs.
Assume that the grah vertices are numbered 1 through n.
Print a single integer — the answer to George's question.
For more information about directed graphs, please visit: http://en.wikipedia.org/wiki/Directed_graph
In the first sample the graph already is interesting, its center is vertex 3.