【編程題解】Count number

Description

In an undirected connected graph, if an edge is deleted and the graph is divided into two disconnected parts, the edge is called a cut edge.

Find the number of undirected connected graphs satisfying the following conditions:

1. It is composed of N nodes with labeled Numbers ranging from 1 to N.

2. Cut edges are less than M.

3. No loop and multiple edges .

 

Input

The input is one line and contains two integers N and M.

Data range:2≤N≤50,0≤M≤N∗(N−1)/2

 

Output

Output an integer to represent the number of unconnected graphs that meet the conditions after taking the modulus of 10^9+7.

Sample Input 1 

3 3

Sample Output 1

4

 

Personal Answer  (using language：JAVA)  Not necessarily right

public class Main {
    public static void main(String[] args) {
        System.out.println("Unsolved");
    }
}

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