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.*;
import java.util.*;
import java.math.*;
import java.util.function.*;
import java.util.stream.*;
import static java.util.Arrays.*;
import static java.lang.Math.*;
import static java.lang.System.arraycopy;
import static java.lang.Integer.parseInt;
import static java.lang.Long.parseLong;

public class Main {

	public static void main(String[] args) {
		MyScanner sc = new MyScanner(System.in);
		PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));

		int n = sc.nextInt();

		HashMap<Long, Long> counts = new HashMap<>(n);
		long count = 0L;
		long accum = 0L;
		BigInteger sum = BigInteger.ZERO;

		for (int i = 0; i < n; i++) {
			long a = sc.nextLong();
			long c, subc = 0L, suba = 0L;

			c = counts.getOrDefault(a - 1, 0L);
			subc += c;
			suba += (a - 1) * c;
			
			c = counts.getOrDefault(a + 1, 0L);
			subc += c;
			suba += (a + 1) * c;
			
			c = counts.getOrDefault(a, 0L);
			subc += c;
			suba += a * c;
			
			sum = sum.add(BigInteger.valueOf(a * (count - subc) - (accum - suba)));
			accum += a;
			count++;
			counts.put(a, c + 1);
		}

		out.println(sum);

		out.close();
	}

  static class MyScanner {
        public BufferedReader reader;
        public StringTokenizer tokenizer = null;
        public MyScanner(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
        }
        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try { tokenizer = new StringTokenizer(reader.readLine()); }
                catch (IOException e) { throw new RuntimeException(e); }
            }
            return tokenizer.nextToken();
        }
        public int nextInt() { return Integer.parseInt(next()); }
        public long nextLong() { return Long.parseLong(next()); }
    }
}

