Score : 100 points
You are given a directed graph with N vertices and M edges, not necessarily simple. The i-th edge is oriented from the vertex a_i to the vertex b_i. Divide this graph into strongly connected components and print them in their topological order.
Input is given from Standard Input in the following format:
N M a_0 b_0 a_1 b_1 : a_{M - 1} b_{M - 1}
Print 1+K lines, where K is the number of strongly connected components. Print K on the first line. Print the information of each strongly connected component in next K lines in the following format, where l is the number of vertices in the strongly connected component and v_i is the index of the vertex in it.
l v_0 v_1 ... v_{l-1}
Here, for each edge (a_i, b_i), b_i should not appear in earlier line than a_i.
If there are multiple correct output, print any of them.
6 7 1 4 5 2 3 0 5 5 4 1 0 3 4 2
4 1 5 2 4 1 1 2 2 3 0