
Given an integer array nums and two integers firstLen and secondLen , return the maximum sum of elements in two non-overlapping subarrays with lengths firstLen and secondLen .
The array with length firstLen could occur before or after the array with length secondLen , but they have to be non-overlapping.
A subarray is a contiguous part of an array.
1 <= firstLen, secondLen <= 10002 <= firstLen + secondLen <= 1000firstLen + secondLen <= nums.length <= 10000 <= nums[i] <= 1000