Next Greater Element

Given an array of integers, your task is to find the next greater element for each element in the array. The next greater element for an element x is the first greater element on the right side of x in the array. If there is no greater element, output -1 for that position. Return the resulting array as space-separated integers. Example: Input: '4 5 2 10', Output: '5 10 10 -1'.