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.FileNotFoundException;
import java.io.FileReader;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Scanner;import org.omg.CORBA.INTERNAL;

public class Main {
	
	
	public static void main(String[] args) throws Exception {
        new Main();
    }
	
	public Main() throws Exception{
		Scanner sc = new Scanner(System.in);
//		Scanner sc = new Scanner(new FileReader("input"));
		

//		System.out.println(Long.MIN_VALUE);
		
		int n = sc.nextInt();
		long[] arr = new long[n];
		long[] sums = new long[n];
		long totalSum = 0;
		HashMap<Long, Long> numbers = new HashMap<>();
		
		for (int i=0;i<n;i++){
			arr[i] = sc.nextLong();
			totalSum+=arr[i];
			if (numbers.containsKey(arr[i])) {
				long count = numbers.get(arr[i]);
				numbers.put(arr[i], count+1);
			} else {
				numbers.put(arr[i], 1L);
			}
			
		}
		
		for (int i=0;i<n;i++) {
			totalSum-=arr[i];
			sums[i] = totalSum;
		}
		
		
		BigInteger sum = new BigInteger("0");
		
		for (int i=0;i<n-1;i++) {
			
			long ans = sums[i] - (n - i - 1) * arr[i];
			
			
			
			numbers.put(arr[i], numbers.get(arr[i]) - 1L);
			long acount = numbers.getOrDefault(arr[i], 0L);
			long aminus1count = numbers.getOrDefault(arr[i]-1L, 0L);
			long aplus1count = numbers.getOrDefault(arr[i]+1L, 0L);
//			System.out.println(acount);
//			System.out.println(aminus1count);
//			System.out.println(aplus1count);
//			System.out.println();
			ans += aminus1count;
			ans -= aplus1count;
			
//			System.out.println(ans);
			sum = sum.add(new BigInteger(ans+""));
			
		}
		System.out.println(sum);
        sc.close();
	}
	
	
	long d (long x, long y){
		long ans = 0;
		if (Math.abs(x-y) > 1) {
			ans = y-x;
		}
		
		
		return ans;
	}
	
	
	
	
	

	
	
	
}
