Once upon a time in a mystical land, there lived a wise sorcerer named Merlin. Merlin possessed a unique power to perceive the hidden patterns in permutations. He was particularly intrigued by the concept of inversions in a permutation.
An inversion in a permutation is a pair of elements () such that i < j and . The number of inversions in a permutation represents how far the permutation is from being sorted in ascending order.
Merlin decided to challenge the talented programmers by posing the following problem: Given a permutation of integers from 1 to n, your task is to calculate the number of inversions present in the permutation.
Input
The first line contains a single integer n (1 β€ n β€ 100 000), representing the size of the permutation. The second line contains n space-separated integers, representing the elements of the permutation.
Output
Print a single integer, representing the number of inversions in the given permutation.