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.Scanner;
import java.util.Map;
import java.util.HashMap;
public class Main {
	
	public static void main(String arg[]){
		Scanner scan= new Scanner(System.in);
		long n=scan.nextLong();
		long[] ara= new long[(int) n];
		for(long i=0L;i<n;i++) {
			ara[(int)i]=scan.nextLong();
		}
		BigInteger ans,totalsum;
		ans = BigInteger.valueOf(0);
		totalsum = BigInteger.valueOf(0);
		
		Map<BigInteger,BigInteger> sum= new HashMap<BigInteger,BigInteger>();
		for(int i=0;i<n;i++) {
			BigInteger temp=new BigInteger(ara[i]+"");
			
			if(sum.containsKey(temp))sum.put(temp,sum.get(temp).add(new BigInteger("1")));
			else sum.put(temp,new BigInteger("1"));
			
			totalsum=totalsum.add(temp);
			BigInteger a,b,c;
			if(sum.containsKey(temp.add(new BigInteger("1"))))a= sum.get(temp.add(new BigInteger("1")));
			else a=new BigInteger("0");
			if(sum.containsKey(temp))b= sum.get(temp);
			else b=new BigInteger("0");
			if(sum.containsKey(temp.subtract(new BigInteger("1"))))c= sum.get(temp.subtract(new BigInteger("1")));
			else c=new BigInteger("0");
			BigInteger total=BigInteger.valueOf(i+1);
			total=total.subtract(a).subtract(b).subtract(c);
			BigInteger minus = new BigInteger("0");
			minus=minus.add(a.multiply(temp.add(new BigInteger("1"))));
			minus=minus.add(b.multiply(temp));
			minus=minus.add(c.multiply(temp.subtract(new BigInteger("1"))));
			ans=ans.add(total.multiply(temp));
			//System.out.println(ans);
			ans=ans.subtract(totalsum.subtract(minus));
			//System.out.println(ans);

			
		}
		System.out.println(ans);
		scan.close();
	}
	
}
