Let's denote a function 

<image>

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. 
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.*;

public class Coba {
    static final int MAX = (int) 2e5;
    static int N;
    static int[] arr = new int[MAX+5];
    static BigInteger ans = new BigInteger("0");
    static long sum = 0;
    static Map<Integer,Integer> cnt = new HashMap<>();

    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));

        N = Integer.valueOf(br.readLine());
        StringTokenizer token = new StringTokenizer(br.readLine());
        for (int i=0; i < N; i++) {
            arr[i] = Integer.valueOf(token.nextToken());
            sum += arr[i];

            if (!cnt.containsKey(arr[i])) cnt.put(arr[i], 0);
            cnt.put(arr[i], cnt.get(arr[i]) + 1);
        }


        for (int i = 0; i < N; i++) {
            ans = ans.add(new BigInteger(Long.toString(sum - ((long)arr[i]) * (N-i))));
            ans = ans.add(new BigInteger(Integer.toString(cnt.containsKey(arr[i] + 1) ? -cnt.get(arr[i] + 1) : 0)));
            ans = ans.add(new BigInteger(Integer.toString(cnt.containsKey(arr[i] - 1) ? cnt.get(arr[i] - 1) : 0)));

            sum -= arr[i];
            cnt.put(arr[i], cnt.get(arr[i]) - 1);
        }

        out.println(ans);
        out.close();
    }
}