Let's denote a function 

<image>

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.*;


public class Main {
	public static Map<Long, Integer> counts = new HashMap();
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		BigInteger sum = new BigInteger(new Integer(0).toString());
		long x;
		long n;
		BigInteger ans = new BigInteger("0");
		Scanner input = new Scanner(System.in);
		n = input.nextLong();
		for(int i = 0; i < n; ++i)
		{
			x = input.nextLong();
			BigInteger tmp1 = 
					new BigInteger(new Integer(i - (counts.containsKey(x)? counts.get(x):0)
							- (counts.containsKey(x-1)? counts.get(x-1):0)
							-(counts.containsKey(x+1)? counts.get(x+1):0)).toString()).multiply(new BigInteger(new Long(x).toString()));
			BigInteger tmp2 = sum.subtract(new BigInteger(new Long((counts.containsKey(x)? counts.get(x):0) * x
							+ (counts.containsKey(x-1)? counts.get(x-1):0) * (x-1)
							+ (counts.containsKey(x+1)? counts.get(x+1):0) * (x+1)).toString()));
			ans = ans.add(tmp1.subtract(tmp2));
			int val = counts.containsKey(x) ? counts.get(x) : 0;
			counts.put(x, val + 1);
			sum = sum.add(new BigInteger(new Long(x).toString()));
		}
		System.out.println(ans);
		
	}

}

