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

public class REDD2_BI {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		PrintWriter writer = new PrintWriter(System.out);
		int n = scanner.nextInt();
		long[] array = new long[n];
		for (int i = 0; i <= array.length - 1; ++i) {
			array[i] = scanner.nextLong();
		}
		BigInteger result = BigInteger.ZERO;
		long prefixSum = 0l;
		HashMap<Long, Long> map = new HashMap<>();
		map.put(array[n - 1], Long.valueOf(1));
		for (int i = array.length - 2; i >= 0; --i) {

			if (map.containsKey(array[i])) {
				map.put(array[i], map.get(array[i]) + 1);
			} else {
				map.put(array[i], Long.valueOf(1));
			}

			prefixSum = prefixSum + array[i + 1];

			Long numLess = map.get(array[i] - 1);
			if (numLess == null) {
				numLess = Long.valueOf(0);
			}
			Long numEqual = map.get(array[i]);
			if (numEqual == null) {
				numEqual = Long.valueOf(0);
			} else {
				numEqual = numEqual - 1;
			}
			Long numGreater = map.get(array[i] + 1);
			if (numGreater == null) {
				numGreater = Long.valueOf(0);
			}

			long a = ((array[i] - 1) * numLess) + (array[i] * numEqual) + ((array[i] + 1) * numGreater);
			long in = numLess + numEqual + numGreater;
			long b = array[i] * Math.abs(in - ((n - 1) - i));
			long c = prefixSum - a - b;

			result = result.add(BigInteger.valueOf(c));

		}
		scanner.close();
		writer.println(result.toString());
		writer.flush();
		writer.close();
	}
}
