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.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.HashMap;
import java.util.StringTokenizer;

public class D
{
	public static void main(String[] args) throws IOException
	{
		Scanner sc = new Scanner(System.in);
		PrintWriter pw = new PrintWriter(System.out);
		int n = sc.nextInt();
		int[] arr = new int[n];
		for (int i = 0; i < n; i++)
			arr[i] = sc.nextInt();
		HashMap<Integer, Integer> map = new HashMap<>();
		BigInteger ans = new BigInteger("0");
		long sum = 0;
		for (int i = 0; i < n; i++)
		{
			long cnt = i;
			Integer x = map.get(arr[i] + 1);
			if(x != null)
				cnt -= x;
			x = map.get(arr[i] - 1);
			if(x != null)
				cnt -= x;
			ans = ans.add((new BigInteger(""+cnt).multiply(new BigInteger(""+arr[i]))));
			ans = ans.subtract(new BigInteger(""+sum));
			x = map.get(arr[i] + 1);
			if(x != null)
				ans = ans.add(new BigInteger("" + (1l * (arr[i] + 1) * x)));
			x = map.get(arr[i] - 1);
			if(x != null)
				ans = ans.add(new BigInteger("" + (1l * (arr[i] - 1) * x)));
			sum += arr[i];
			if(!map.containsKey(arr[i]))
				map.put(arr[i], 1);
			else
				map.put(arr[i], map.get(arr[i]) + 1);
		}
		pw.println(ans);
		pw.flush();
	}

	static class Scanner
	{
		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s)
		{
			br = new BufferedReader(new InputStreamReader(s));
		}

		public String next() throws IOException
		{
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}

		public int nextInt() throws IOException
		{
			return Integer.parseInt(next());
		}

		public long nextLong() throws IOException
		{
			return Long.parseLong(next());
		}

		public String nextLine() throws IOException
		{
			return br.readLine();
		}

		public double nextDouble() throws IOException
		{
			return Double.parseDouble(next());
		}

		public boolean ready() throws IOException
		{
			return br.ready();
		}
	}
}
