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from collections import deque, defaultdict
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def can_finish(n, edges):
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    graph = defaultdict(list)
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    indeg = [0] * n
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    for a, b in edges:
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        graph[b].append(a)
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        indeg[a] += 1
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    q = deque([i for i in range(n) if indeg[i] == 0])
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    seen = 0
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    while q:
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        x = q.popleft()
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        seen += 1
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        for y in graph[x]:
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            indeg[y] -= 1
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            if indeg[y] == 0:
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                q.append(y)
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    return seen == n