D. Almost Differencetime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard outputLet'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.InputThe 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. OutputPrint one integer — the sum of d(ai, aj) over all pairs (i, j) such that 1 ≤ i ≤ j ≤ n.ExamplesInput51 2 3 1 3Output4Input46 6 5 5Output0Input46 6 4 4Output-8NoteIn the first example:  d(a1, a2) = 0;  d(a1, a3) = 2;  d(a1, a4) = 0;  d(a1, a5) = 2;  d(a2, a3) = 0;  d(a2, a4) = 0;  d(a2, a5) = 0;  d(a3, a4) =  - 2;  d(a3, a5) = 0;  d(a4, a5) = 2. 
Input51 2 3 1 3
Output4
['data structures', 'math', '*2200']