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.util.HashMap;
import java.util.Scanner;
import java.math.BigInteger; 

public class Main {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int n = s.nextInt();
		BigInteger ans = new BigInteger("0");
		long[] arr = new long[n];
		for(int i = 0; i < n; i++) {
			arr[i] = s.nextLong();
		}
		HashMap<Long, Integer> map = new HashMap<Long, Integer>();
		for(int i = 0; i < n; i++) {
			long temp = 0;
			if(map.containsKey(arr[i])) {
				temp += map.get(arr[i]);
			}
			if(map.containsKey(arr[i] - 1)) {
				temp += map.get(arr[i] - 1);
			}
			if(map.containsKey(arr[i] + 1)) {
				temp += map.get(arr[i] + 1);
			}
			ans = ans.add(BigInteger.valueOf((i - temp) * arr[i]));
			map.put(arr[i], map.containsKey(arr[i]) ? (map.get(arr[i]) + 1) : 1);
		}
		map = new HashMap<Long, Integer>();
		for(int i = n - 1; i >= 0; i--) {
			long temp = 0;
			if(map.containsKey(arr[i])) {
				temp += map.get(arr[i]);
			}
			if(map.containsKey(arr[i] - 1)) {
				temp += map.get(arr[i] - 1);
			}
			if(map.containsKey(arr[i] + 1)) {
				temp += map.get(arr[i] + 1);
			}
			ans = ans.subtract(BigInteger.valueOf((n - 1 - i - temp) * arr[i]));
			map.put(arr[i], map.containsKey(arr[i]) ? (map.get(arr[i]) + 1) : 1);
		}
		System.out.println(ans);
	}

}
