29 lines
550 B
Python
29 lines
550 B
Python
N = int(input())
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P = []
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last = 1
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while N != 0:
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if 2*N > last:
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if last == 1:
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last = 2
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for i in range(last, 2*N+1):
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for p in P:
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if i % p == 0:
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break
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elif p ** 2 > i:
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P.append(i)
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break
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else:
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P.append(i)
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c = 0
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for p in P:
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if N < p <= 2 * N:
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c += 1
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elif p > 2*N:
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break
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if last < 2*N:
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last = 2*N
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print(c)
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N = int(input())
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