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D. Almost Difference
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

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.

Input

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.

Output

Print one integer — the sum of d(ai, aj) over all pairs (i, j) such that 1 ≤ i ≤ j ≤ n.

Examples
Input
5
1 2 3 1 3
Output
4
Input
4
6 6 5 5
Output
0
Input
4
6 6 4 4
Output
-8
Note

In the first example:

  1. d(a1, a2) = 0;
  2. d(a1, a3) = 2;
  3. d(a1, a4) = 0;
  4. d(a1, a5) = 2;
  5. d(a2, a3) = 0;
  6. d(a2, a4) = 0;
  7. d(a2, a5) = 0;
  8. d(a3, a4) =  - 2;
  9. d(a3, a5) = 0;
  10. d(a4, a5) = 2.