Given an arraynums, we call(i, j)animportant reverse pairifi < jandnums[i] > 2*nums[j].

You need to return the number of important reverse pairs in the given array.

Example1:

Input: [1,3,2,3,1]

Output: 2

Example2:

Input: [2,4,3,5,1]

Output: 3

Note:

1. The length of the given array will not exceed50,000
2. All the numbers in the input array are in the range of 32-bit integer.