Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.

Given nums = [-2, 0, 3, -5, 2, -1]

sumRange(0, 2) -> 1
sumRange(2, 5) -> -1
sumRange(0, 5) -> -3

• You may assume that the array does not change.

• There are many calls to sumRange function.