Find the Pivot Integer
Given a positive integer n, find the pivot integer x such that:
- The sum of all elements between
1andxinclusively equals the sum of all elements betweenxandninclusively.
Return the pivot integer x. If no such integer exists, return -1. It is guaranteed that there will be at most one pivot index for the given input.
Example 1
Input
n = 8Output
66 is the pivot integer since 1 + 2 + 3 + 4 + 5 + 6 = 6 + 7 + 8 = 21.
Example 2
Input
n = 1Output
11 is the pivot integer since 1 = 1.
Constraints
- 1 <= n <= 1000
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