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55 lines
903 B
Python
55 lines
903 B
Python
"""
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By listing the first six prime numbers:
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2, 3, 5, 7, 11, and 13
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We can see that the 6th prime is 13. What is the Nth prime number?
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"""
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from math import sqrt
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def isprime(n):
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if n == 2:
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return True
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elif n % 2 == 0:
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return False
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else:
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sq = int(sqrt(n)) + 1
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for i in range(3, sq, 2):
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if n % i == 0:
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return False
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return True
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def solution(n):
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"""Returns the n-th prime number.
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>>> solution(6)
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13
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>>> solution(1)
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2
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>>> solution(3)
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5
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>>> solution(20)
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71
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>>> solution(50)
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229
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>>> solution(100)
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541
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"""
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i = 0
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j = 1
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while i != n and j < 3:
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j += 1
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if isprime(j):
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i += 1
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while i != n:
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j += 2
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if isprime(j):
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i += 1
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return j
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if __name__ == "__main__":
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print(solution(int(input().strip())))
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