Let's denote a function
You are given an array a consisting of n integers. You have to calculate the sum of d(a_{i}, a_{j}) 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 a_{1}, a_{2}, ..., a_{n} (1 ≤ a_{i} ≤ 10^{9}) — elements of the array.
Print one integer — the sum of d(a_{i}, a_{j}) over all pairs (i, j) such that 1 ≤ i ≤ j ≤ n.
5
1 2 3 1 3
4
4
6 6 5 5
0
4
6 6 4 4
-8
In the first example:
Name |
---|