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.*;
import java.math.BigInteger;
import java.util.HashMap;
import java.util.Scanner;
import java.util.TreeMap;

public class D {
	public static void main(String argv[]) {
		Scanner scan = new Scanner(System.in);
		TreeMap<Long, Integer> mp = new TreeMap<Long, Integer>();
		int n = scan.nextInt();
		long a[] = new  long[n];
		for(int i=0;i<n;i++) {
			a[i] = scan.nextLong();
			//System.out.println(arr[i]);
		}
		BigInteger ans  = new BigInteger("0");
		long sum = 0;
		for(int i=0;i<n;i++) {
			int num1 = 0,num2 = 0,num3 = 0;
			if(mp.containsKey(a[i]+1)) {
				num2 = mp.get(a[i]+1);
			}
			if(mp.containsKey(a[i]-1)) {
				num3 = mp.get(a[i]-1);
			}
			if(mp.containsKey(a[i])) {
				num1 = mp.get(a[i]);
			}
			//System.out.println("sum1 = "+num1+"sum2 = "+num2+"sum3 = "+num3);
			long tmp = sum - num1 * a[i] - (a[i] + 1) * num2 - (a[i] - 1) * num3;
			//System.out.println("tmp = "+tmp);
			
			BigInteger tmp2 = BigInteger.valueOf(i-num1-num2-num3);
			//System.out.println("tmp2 = "+tmp2);
			tmp2 = tmp2.multiply(BigInteger.valueOf(a[i]));
			//System.out.println("tmp2 = "+tmp2);

			tmp2 = tmp2.subtract(BigInteger.valueOf(tmp));
			//System.out.println("tmp2 = "+tmp2);

			ans = ans.add(tmp2);
			sum+=a[i];
			//System.out.println("ans = "+ans+"sum = "+sum+"tmp = "+tmp);
			//System.out.println();
			if(!mp.containsKey(a[i])) {
				mp.put(a[i], 1);
			}
			else {
				mp.put(a[i], mp.get(a[i])+1);
			}
		}
		System.out.println(ans);
	}
}
