2485. Find the Pivot Integer

Easy

10 Points

Math

Prefix Sum

Given a positive integer n, find the pivot integer x such that: 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.

Examples

Example 1

Input: n = 8 Output: 6 Explanation: 6 is the pivot integer since: 1 + 2 + 3 + 4 + 5 + 6 = 6 + 7 + 8 = 21.

Example 2

Input: n = 1 Output: 1 Explanation: 1 is the pivot integer since: 1 = 1.

Example 3

Input: n = 4 Output: -1 Explanation: It can be proved that no such integer exist.

Constraints

1 <= n <= 1000