Finally, for the most critical subsystem, Rakib needs to identify tightly-coupled clusters of servers where every machine can reach every other machine in the same cluster (directed connections only). Given a directed graph with N nodes and M edges, print the number of strongly connected components (SCCs) — maximal sets of nodes where every node can reach every other node in the set.
Input
Line1: N M. Next M lines: u v (directed edge u→v).
Output
Number of strongly connected components.
Constraints
1 ≤ N ≤ 10^5, 0 ≤ M ≤ 2×10^5
Sample Input
5 5 1 2 2 3 3 1 3 4 4 5
Sample Output
3
main.c
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