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.util.*;
import java.io.*;
import java.math.*;
public class EdE {
	static Set<ArrayList<Integer>> seen;
	public static void main(String[] args) throws Exception{
		int num = 998244353;

		// TODO Auto-generated method stub
 		BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
 		PrintWriter out = new PrintWriter(System.out);
 		int n = Integer.parseInt(bf.readLine());
 		long[] array = new long[n];
 		StringTokenizer st = new StringTokenizer(bf.readLine());
 		Map<Long, ArrayList<Integer>> mp = new HashMap<Long, ArrayList<Integer>>();
 		for(int j =0;j<n;j++){
 			array[j] = Long.parseLong(st.nextToken());
 			mp.put(array[j],  new ArrayList<Integer>());
 		}
 		for(int j= 0;j<n;j++)
 			mp.get(array[j]).add(j);
 		for(long j: mp.keySet())
 			Collections.sort(mp.get(j));
 		long sum = 0;
 		int index = 0;
 		BigInteger ans = BigInteger.valueOf(0);
 		for(long j = -(n-1);j<=(n-1);j+=2){
 			ans = ans.add(BigInteger.valueOf(j*array[index]));
 			index++;
 		}
 		for(int j = 0;j<n;j++){
 			long indexp1 = 0;
 			long indexn1 = 0;
 			if (mp.containsKey(array[j]+1))
 				indexp1 = mp.get(array[j]+1).size() - upperBound(mp.get(array[j]+1), j, 0, mp.get(array[j]+1).size());
 			if (mp.containsKey(array[j]-1))
 				indexn1 = mp.get(array[j]-1).size() - upperBound(mp.get(array[j]-1), j, 0, mp.get(array[j]-1).size());
 			ans = ans.subtract(BigInteger.valueOf(indexp1));
 			ans = ans.add(BigInteger.valueOf(indexn1));
 		}
 		out.println(ans);
 		
 		
 		
 		out.close();
 	}
	public static int upperBound(ArrayList<Integer> array, int target, int l, int r){
		if (target >= array.get(array.size()-1))
			return array.size();
		else if (target < array.get(0))
			return 0;
		int mid = -1;
		while (l<r){
			mid = (l+r)/2;
			if (array.get(mid) > target && (mid-1 < 0 || array.get(mid-1) <= target))
				return mid;
			else if (array.get(mid) > target)
				r = mid;
			else
				l = mid+1;
		}
		return mid;
		
	}
}
 	
 
//StringJoiner sj = new StringJoiner(" "); 
//sj.add(strings)
//sj.toString() gives string of those stuff w spaces or whatever that sequence is

 		
 		
 		
 		
	


