2016. Maximum Difference Between Increasing Elements

class Solution {
public:
    int maximumDifference(vector<int>& nums) {
        int n=nums.size();
        int p=nums[n-1];
        int max=0,max1=0;
        for(int i=n-2;i>=0;i--)
        {
            max1=p-nums[i];
            if(max1>max)
            {
                max=max1;
            }
          if(p<nums[i])
          {
             p=nums[i];
          }  
        }
        if(max==0) return -1;
        return max;
        
    }
};