2017-10-24 15:41:19 +00:00
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# -*- coding: utf-8 -*-
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'''
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Problem:
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The sum of the squares of the first ten natural numbers is,
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1^2 + 2^2 + ... + 10^2 = 385
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The square of the sum of the first ten natural numbers is,
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(1 + 2 + ... + 10)^2 = 552 = 3025
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Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 − 385 = 2640.
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Find the difference between the sum of the squares of the first N natural numbers and the square of the sum.
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'''
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2017-11-25 09:23:50 +00:00
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from __future__ import print_function
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2017-10-24 15:41:19 +00:00
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n = int(input())
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suma = n*(n+1)/2
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suma **= 2
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sumb = n*(n+1)*(2*n+1)/6
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2017-11-25 09:23:50 +00:00
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print(suma-sumb)
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