Maximize the Total Height of Unique Towers

Description

You are given an array maximumHeight, where maximumHeight[i] denotes the maximum height the ith tower can be assigned.

Your task is to assign a height to each tower so that:

- The height of the ith tower is a positive integer and does not exceed maximumHeight[i].

- No two towers have the same height.

Return the maximum possible total sum of the tower heights. If it's not possible to assign heights, return -1.