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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
import java.util.HashMap;
import java.util.HashSet;
import java.util.StringTokenizer;

public class P903D {
	
	public static void main(String[] args) throws IOException {
		
		BufferedReader f = new BufferedReader(new InputStreamReader(System.in));
		
		HashMap<Integer, Integer> count = new HashMap<>();
		HashSet<Integer> hs = new HashSet<>();
		
		int n = Integer.parseInt(f.readLine());
		
		StringTokenizer str = new StringTokenizer(f.readLine());
		
		BigInteger val1 = new BigInteger("0");
		BigInteger val2 = new BigInteger("0");
		
		for(int i = 0; i < n; i++) {
			
			int current = Integer.parseInt(str.nextToken());
			
			if(hs.add(current)) {
				count.put(current, 1);
			} else {
				count.put(current, count.get(current)+1);
			}
			
			if(hs.contains(current-1)) {
				val1 = val1.subtract(new BigInteger(count.get(current-1).toString()));
			}
			
			if(hs.contains(current+1)) {
				val1 = val1.add(new BigInteger(count.get(current+1).toString()));
			}
			
			Long add = new Long(((long) (-1L)*((long) (((long) n) - 1L)) + (long) 2L*((long) i))*((long) current));
			
			val2 = val2.add(new BigInteger(add.toString()));
			
		}
		
		System.out.println(val2.add(val1));
		
		f.close();
		
	}
	
}