2018-10-19 12:48:28 +00:00
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from __future__ import print_function
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# n - no of nodes, m - no of edges
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2018-10-20 19:45:08 +00:00
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n, m = list(map(int,input().split()))
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2018-10-19 12:48:28 +00:00
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g = [[] for i in range(n)] #graph
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r = [[] for i in range(n)] #reversed graph
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# input graph data (edges)
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for i in range(m):
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2018-10-20 19:45:08 +00:00
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u, v = list(map(int,input().split()))
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2018-10-19 12:48:28 +00:00
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g[u].append(v)
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r[v].append(u)
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stack = []
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visit = [False]*n
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scc = []
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component = []
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def dfs(u):
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global g, r, scc, component, visit, stack
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if visit[u]: return
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visit[u] = True
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for v in g[u]:
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dfs(v)
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stack.append(u)
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def dfs2(u):
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global g, r, scc, component, visit, stack
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if visit[u]: return
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visit[u] = True
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component.append(u)
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for v in r[u]:
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dfs2(v)
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def kosaraju():
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global g, r, scc, component, visit, stack
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for i in range(n):
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dfs(i)
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visit = [False]*n
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for i in stack[::-1]:
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if visit[i]: continue
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component = []
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dfs2(i)
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scc.append(component)
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return scc
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print(kosaraju())
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