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.text.SimpleDateFormat;
import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class Main {
	public static void main(String[] args) {
		Map<BigInteger, Integer> mp = new HashMap<>();
		Scanner input = new Scanner(System.in);
		int n = input.nextInt();
		BigInteger sum = new BigInteger("0");
		BigInteger ans = new BigInteger("0");
		for (int i = 1; i <= n; ++i) {
			BigInteger now = input.nextBigInteger();
			sum = sum.add(now);
			if (mp.containsKey(now))
				mp.put(now, mp.get(now) + 1);
			else mp.put(now, 1);
			BigInteger t = sum;		
			int be = 0, mid = 0, en = 0;
			if (mp.containsKey(now.subtract(BigInteger.ONE))) be = mp.get(now.subtract(BigInteger.ONE));
			mid = mp.get(now);
			if (mp.containsKey(now.add(BigInteger.ONE))) en = mp.get(now.add(BigInteger.ONE));
			t = t.subtract(now.subtract(BigInteger.ONE).multiply(BigInteger.valueOf(be)));
			t = t.subtract(now.multiply(BigInteger.valueOf(mid)));
			t = t.subtract(now.add(BigInteger.ONE).multiply(BigInteger.valueOf(en)));
			ans = ans.add(BigInteger.valueOf(i - be - mid - en).multiply(now).subtract(t));
			//System.out.println(BigInteger.valueOf(i - be - mid - en).multiply(now).subtract(t));
		}
		System.out.println(ans);
	}
}