Simple python solution
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```\nclass Solution:\n    def maximumDifference(self, nums: List[int]) -> int:\n        m=0\n        k=0\n        for i in range(len(nums)):\n            for j in range(i+1,len(nums)):\n                if nums[j]>nums[i]:\n                    k=nums[j]-nums[i]\n                    if k>=m:\n                        m=k\n        if m==0:\n            return -1\n        return m\n```
['Python3']