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. 
//package Abumra;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.lang.reflect.Array;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.MathContext;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.StringTokenizer;


public class Main{
	public static void main(String[] args) throws IOException{
		Scanner sc = new Scanner(System.in);
		PrintWriter pw = new PrintWriter(System.out);
		
		BigInteger ans = BigInteger.ZERO;
		int n = sc.nextInt();
		int arr[] = new int[n];
		long cum[] = new long[n];
		
		for (int i = 0; i < n; i++) arr[i] = sc.nextInt();
				
		for (int i = 0; i < cum.length; i++)
		{
			cum[i] = arr[i];
			if(i > 0)
				cum[i] += cum[i-1];
		}
		
		for (int i = 0; i < n; i++)
			ans = ans.add(BigInteger.valueOf((1l*(i+1)*arr[i] - cum[i])));
		
		HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
		for (int i = 0; i < n; i++)
		{
			ans =  ans.subtract(BigInteger.valueOf(map.getOrDefault(arr[i]-1, 0)));
			ans = ans.add(BigInteger.valueOf(map.getOrDefault(arr[i]+1, 0)));
			map.put(arr[i], map.getOrDefault(arr[i], 0)+1);
		}
		System.out.println(ans.toString());
	}
}
