Find Rotation Point

You have a sorted array that has been rotated at an unknown pivot. Write a program that finds the index of the rotation point, where the largest element is located. If the array is not rotated, return -1. The input will be a single line of integers separated by spaces. The output should be a single integer, the index of the rotation point, or -1 if not found. Example: Input: 5 6 7 8 9 1 2 3 4 Output: 4