- Time limit: 1.00 s
- Memory limit: 512 MB
Given an undirected graph, your task is to choose a direction for each edge so that in the resulting directed graph each node has an even outdegree. The outdegree of a node is the number of edges coming out of that node.
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
4 4 1 2 2 3 3 4 1 4
1 2 3 2 3 4 1 4