A graph is given in a file. Every line in the file is a pair of vertices
corresponding to an edge of the graph. Every vertex is represented by an
integer but the vertices may not be numbered consecutively. There is no
limitation on the number of lines in the file. For example the complete
graph with 3 vertices could be represented as:

2 3
2 7
3 7

Write a program using the STL that 

1. reads the graph from the file
2. counts the number of edges
3. counts the number of vertices
4. determines the set of vertices
5. determines the largest degree of the vertices

For example the output for the set given above would be:

1.
2. 3
3. 3
4. 2 3 7
5. 2