import bisect
class Solution(object):
    def reversePairs(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        n = len(nums)
        ans = 0
        bst = []
        for num in nums:
            right = 2 * num
            idx = bisect.bisect_right(bst, right)
            ans += len(bst) - idx
            bisect.insort(bst, num)
        return ans
            