15 lines
345 B
Python
15 lines
345 B
Python
numbers = []
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while True :
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n = int(input())
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if n==0 :
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break
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numbers.append(n)
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M = 2* max(numbers)
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bool_primes = [False]*2 + [True]*(M-1)
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for idx,b in enumerate(bool_primes) :
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if b:
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for j in range(idx**2,M+1,idx) :
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bool_primes[j] = False
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for n in numbers :
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print(bool_primes[n+1:2*n+1].count(True))
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