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.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class D {

	public static final int N = 100100;

	
	public static void main(String[] args){
		
		Scanner sc = new Scanner(System.in);
		
		Integer n = sc.nextInt();
		
		Integer arr[] = new Integer [n];
		
		
		Map< Integer, Integer> map = new HashMap<Integer, Integer>();
		
		BigInteger tot = BigInteger.ZERO;
		for(int i = 0; i<n; i++){
			arr[i] = sc.nextInt();
			tot = tot.add(BigInteger.valueOf(arr[i].intValue()));
			
			Integer count = map.get(arr[i]);
			if (count == null) {
			    map.put(arr[i], 1);
			}
			else {
			    map.put(arr[i], count + 1);
			}
		}
		
		
		BigInteger ans = BigInteger.ZERO;
		
		BigInteger aux = new BigInteger(n.toString());
		for(int i = 0; i<n; i++){
			
			
			BigInteger val = (BigInteger.valueOf(arr[i].intValue()).multiply(aux));
		
			ans = ans.add(tot);
			ans = ans.subtract(val);
			
			
			Integer count = map.get(arr[i] + 1);
			if (count != null) {
			    ans = ans.subtract(BigInteger.valueOf(count.intValue()));
			}
			
			count = map.get(arr[i] - 1);
			if (count != null) {
			    ans = ans.add(BigInteger.valueOf(count.intValue()));
			}
			
		
			int v = map.get(arr[i]);
			map.put(arr[i].intValue(), v-1);
			
			aux = aux.subtract(BigInteger.ONE);
			tot = tot.subtract(BigInteger.valueOf(arr[i].intValue()));
		}
		
		System.out.println(ans);
		
		
	}
	
	
}



