Given an array of integers arr, find the sum of min(b) , where b ranges over every (contiguous) subarray of arr . Since the answer may be large, return the answer modulo 10 ^9 + 7 .
Examples
Example 1
Input: arr = [3,1,2,4]
Output: 17
Subarrays are [3], [1], [2], [4], [3,1], [1,2], [2,4], [3,1,2], [1,2,4], [3,1,2,4].
Minimums are 3, 1, 2, 4, 1, 1, 2, 1, 1, 1.
Sum is 17.
