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.InputStream;
import java.util.Scanner;
import java.util.HashMap;
import java.math.BigInteger;
import java.lang.Integer;

public class P903D_AlmostDifference {
	public static void main(String[] args){
		Scanner scanner = new Scanner(System.in);
		HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
		
		Integer n, ai;
		BigInteger sum = BigInteger.valueOf(0), sub = BigInteger.valueOf(0);
		n = (Integer)scanner.nextInt();

		for (int i=0; i<n; i++){
			ai = (Integer)scanner.nextInt();
			BigInteger big_ai = BigInteger.valueOf(ai);
			sum = sum.add(big_ai.multiply(BigInteger.valueOf(-(n - 1 - 2*i))));
			if (!map.containsKey(ai)){
				map.put(ai,1);
			}
			else{
				map.put(ai, map.get(ai) + 1);
			}
			// System.out.println("There are " + map.get(ai) + " instances of " + ai);

			if (ai > 1 && map.containsKey(ai-1)){
				sub = sub.add(BigInteger.valueOf(map.get(ai-1)));
			}
			if (ai < 1000000000 && map.containsKey(ai+1)){
				sub = sub.add(BigInteger.valueOf(-map.get(ai+1)));
			}

		}
		
		System.out.println(sum.subtract(sub));
	}
}