- Time limit: 1.00 s
- Memory limit: 512 MB
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 integers $a$ and $b$: there is an edge between nodes $a$ and $b$.
You may assume that the graph is simple, i.e., there is at most one edge between any two nodes and every edge connects two distinct nodes.
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.
If there are no solutions, only print "IMPOSSIBLE".
- $1 \le n \le 10^5$
- $1 \le m \le 2 \cdot 10^5$
- $1 \le a,b \le n$