#5578. CSES2078 欧拉子图
CSES2078 欧拉子图
Eulerian Subgraphs
You are given an undirected graph that has n nodes and m edges. We consider subgraphs that have all nodes of the original graph and some of its edges. A subgraph is called Eulerian if each node has even degree. Your task is to count the number of Eulerian subgraphs modulo 10^9+7.
Input
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 that describe the edges. Each line has two integers a and b: there is an edge between nodes a and b. There is at most one edge between two nodes, and each edge connects two distinct nodes.
Output
Print the number of Eulerian subgraphs modulo 10^9+7.
Constraints
\cdot 10^5$
Example
Input
4 3
1 2
1 3
2 3
Output
2
Explanation: You can either keep or remove all edges, so there are two possible Eulerian subgraphs.