Given an undirected graph, your task is to choose a direction for each edge so that the resulting directed graph is acyclic.
The first input line has two integers $n$ and $m$ : the number of nodes and edges. The nodes are numbered $1,2,\dots,n$ .
After this, there are $m$ lines describing the edges. Each line has two distinct integers $a$ and $b$ : there is an edge between nodes $a$ and $b$ .
Print $m$ lines describing the directions of the edges. Each line has two integers $a$ and $b$ : there is an edge from node $a$ to node $b$ . You can print any valid solution.
3 3 1 2 2 3 3 1· \n · \n · \n · \n
1 2 3 2 3 1· \n · \n · \n