Time Limit: 2 seconds
Memory Limit: 256 megabytes
Let's denote a function
You are given an array a consisting of n integers. You have to calculate the sum of d(ai, aj) over all pairs (i, j) such that 1 ≤ i ≤ j ≤ n.
The first line contains one integer n (1 ≤ n ≤ 200000) — the number of elements in a.
The second line contains n integers a1, a2, ..., an (1 ≤ ai ≤ 109) — elements of the array.
In the first example: