Challenge: Next Greater Element Using a Stack

Problem Statement

You are required to implement the next_greater_element() function. For each element $i$ in a list, the function finds the first element to its right which is greater than element $i$. If for any element such a value does not exist, the answer is -1.

Note: The next greater element is the first element towards the right which is greater than the given element. For example, in the list [1, 3, 8, 4, 10, 5], the next greater element of 3 is 8 and the next greater element for 8 is 10.

Input

An integer list.

Output

A list containing the next greater element of each element from the input list.

Sample Input

list = [4, 6, 3, 2, 8, 1]

Sample Output

result = [6, 8, 8, 8, -1, -1]