36 lines
606 B
Python
36 lines
606 B
Python
import sys
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input = sys.stdin.readline
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n, m = map(int, input().split())
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parents = [i for i in range(n)]
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rank = [0]*n
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def find(x):
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if parents[x] != x:
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parents[x] = find(parents[x])
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return parents[x]
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def union(x, y) :
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x = find(x)
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y = find(y)
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if x == y : return False
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if rank[x] > rank[y] :
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parents[y] = x
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else :
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parents[x] = y
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if rank[x] == rank[y] :
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rank[y] += 1
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return True
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ans = 0
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for i in range(m) :
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a, b = map(int, input().split())
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if not union(a,b) :
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ans = i+1
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break
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print(ans) |