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. 
// Working program with FastReader
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;
import java.util.StringTokenizer;
import java.util.*;
import java.math.*;
public class D3
{
    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;
 
        public FastReader()
        {
            br = new BufferedReader(new
                     InputStreamReader(System.in));
        }
 
        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
 
        int nextInt()
        {
            return Integer.parseInt(next());
        }
 
        long nextLong()
        {
            return Long.parseLong(next());
        }
 
        double nextDouble()
        {
            return Double.parseDouble(next());
        }
 
        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
 
    public static void main(String[] args)
    {
        FastReader s=new FastReader();
        Long n = s.nextLong();
        HashMap<Long, Long> mp = new HashMap<Long, Long>();
        Long ans=0l;
        mp.clear();
        BigInteger ans_big = BigInteger.ZERO;
        BigInteger temp;
        for(Long i=0l;i<n;i++)
        {
            ans = 0l;
            Long x = s.nextLong();
            if(mp.containsKey(x))
            {
                Long val = mp.get(x);
                mp.remove(x);
                mp.put(x,val+1l);
            }
            else
                mp.put(x,1l);
            if(mp.containsKey(x+1))
                ans += mp.get(x+1);
            if(mp.containsKey(x-1))
                ans -= mp.get(x-1);
            ans += x*(2*i+1-n);
            temp = BigInteger.valueOf(ans);
            ans_big = ans_big.add(temp);
        }
        
        System.out.println(ans_big.toString());
    }
}