Let's denote a function 

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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.*;
import java.math.BigInteger;
import java.util.*;

public class Main {

    static StreamTokenizer in;
    static PrintWriter out;

    static int nextInt() throws IOException
    {
        in.nextToken();
        return (int)in.nval;
    }

    public static void main(String[] args) throws IOException {
        in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
        out = new PrintWriter(System.out);
        int n = nextInt();
        BigInteger sum = BigInteger.ZERO;
        long partSum = 0;
        TreeMap<Integer, Integer> numbers = new TreeMap<>();
	    for (int i = 0; i < n; i++) {
            int d = nextInt();
            sum = sum.add(BigInteger.valueOf((long)d * i - partSum));
            // Excluding -1
            if (numbers.get((Integer)(d - 1)) != null)
                sum = sum.subtract(BigInteger.valueOf(numbers.get((Integer)(d - 1))));
            // Excluding +1
            if (numbers.get((Integer)(d + 1)) != null)
                sum = sum.add(BigInteger.valueOf(numbers.get((Integer)(d + 1))));
            // Incrementing number count
            if (numbers.get((Integer)d) != null) {
                int c = numbers.get((Integer)d);
                numbers.put(d, c + 1);
            }
            else
                numbers.put(d, 1);
            partSum += d;
        }
        out.print(sum);
        out.flush();
    }
}