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

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		BigInteger sum = new BigInteger("0");
		Integer n = scan.nextInt();
		HashMap<Long, Long> freq = new HashMap<Long, Long>();
		ArrayList<Long> a = new ArrayList<Long>();
		for (int i = 0; i < n; ++i) {
			Long x;
			x = scan.nextLong();
			a.add(x);
			if (!freq.containsKey(x)) {
				freq.put(x, (long) 1);
			} else {
				freq.put(x, freq.get(x) + 1);
			}
		}
		ArrayList<Long> cum = new ArrayList<Long>(a);
		for (int i = n - 2; i >= 0; --i)
			cum.set(i, cum.get(i) + cum.get(i + 1));
		for (int i = 0; i + 1 < n; ++i) {
			Long fn = new Long(0);
			Long fp = new Long(0);
			Long pr = new Long(a.get(i) + 1);
			Long nx = new Long(a.get(i) - 1);
			if (freq.containsKey(nx)) {
				fn = freq.get(nx);
			}
			if (freq.containsKey(pr)) {
				fp = freq.get(pr);
			}
			Long si = cum.get(i + 1) - fn * nx - fp * pr;
			Long size = n - 1 - i - fn - fp;
			sum = sum.add(BigInteger.valueOf(si - size * a.get(i)));
			freq.put(a.get(i), freq.get(a.get(i)) - 1);
		}
		System.out.println(sum);
		scan.close();
	}
}
