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You are given a convex polygon with N vertices. Find the total
number of parts it is divided by all possible diagonals, assuming that no
three of them intersect at one point.
Input
The first line of input contains one integer
N (3 ≤ N ≤ 50000).
Output
Output a single number – the number of parts.
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Input 1
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Output 1
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3
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1
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Input 2
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Output 2
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4
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4
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