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 $10^9+7$ .
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.
Print the number of Eulerian subgraphs modulo $10^9+7$ .
4 3 1 2 1 3 2 3
· \n · \n · \n · \n
2
\n
You can either keep or remove all edges, so there are two possible Eulerian subgraphs.