Let's denote a function 

<image>

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.math.BigInteger;
import java.util.Arrays;
import java.util.HashMap;
import java.util.StringTokenizer;

public final class Solution implements Closeable, AutoCloseable
{
  void Solve() throws NumberFormatException, IOException
  {
    int n = input.nextInt();
    long[] a = input.readLongArray(n);
    long[] s = new long[n];
    for (int i = n - 2; i >= 0; i--)
      s[i] = s[i + 1] + a[i + 1];
    HashMap<Long, Long> s1 = new HashMap<>();
    HashMap<Long, Integer> c = new HashMap<>();
    for (int i = 0; i < n; i++)
    {
      s1.merge(a[i] - 1, a[i], Long::sum);
      s1.merge(a[i], a[i], Long::sum);
      s1.merge(a[i] + 1, a[i], Long::sum);
      c.merge(a[i] - 1, 1, Integer::sum);
      c.merge(a[i], 1, Integer::sum);
      c.merge(a[i] + 1, 1, Integer::sum);
    }
    BigInteger ans = BigInteger.ZERO;
    for (int i = 0; i < n; i++)
    {
      s1.merge(a[i] - 1, -a[i], Long::sum);
      s1.merge(a[i], -a[i], Long::sum);
      s1.merge(a[i] + 1, -a[i], Long::sum);
      c.merge(a[i] - 1, -1, Integer::sum);
      c.merge(a[i], -1, Integer::sum);
      c.merge(a[i] + 1, -1, Integer::sum);
      long s2 = s[i] - s1.get(a[i]);
      int m = n - i - 1 - c.get(a[i]);
//      ans += s2 - m * a[i];
      BigInteger x = BigInteger.valueOf(m).multiply(BigInteger.valueOf(a[i]));
      ans = ans.add(BigInteger.valueOf(s2).subtract(x));
    }
    output.print(ans);
  }

  private final FastScanner input;
  private final PrintWriter output;

  Solution()
  {
    input = new FastScanner(System.in);
    output = new PrintWriter(System.out);
  }

  public static void main(String[] args) throws IOException
  {
    try (Solution solution = new Solution())
    {
      solution.Solve();
    }
  }

  @Override
  public void close()
  {
    output.flush();
    output.close();
  }

  @SuppressWarnings("unused")
  class FastScanner
  {
    private static final int bufferSize = 64 * 1024;
    private final BufferedReader reader;
    private StringTokenizer tokenizer;

    FastScanner(InputStream inputStream)
    {
      this.reader = new BufferedReader(new InputStreamReader(inputStream), bufferSize);
    }

    String nextToken() throws IOException
    {
      while (tokenizer == null || !tokenizer.hasMoreTokens())
      {
        String line = reader.readLine();
        if (line == null)
        {
          tokenizer = null;
          return null;
        }
        tokenizer = new StringTokenizer(line);
      }
      return tokenizer.nextToken();
    }

    int[] readIntArray(int n) throws IOException
    {
      int[] a = new int[n];
      for (int i = 0; i < n; i++)
      {
        a[i] = nextInt();
      }
      return a;
    }

    long[] readLongArray(int n) throws IOException
    {
      long[] a = new long[n];
      for (int i = 0; i < n; i++)
      {
        a[i] = nextLong();
      }
      return a;
    }

    int nextInt() throws NumberFormatException, IOException
    {
      return Integer.parseInt(nextToken());
    }

    long nextLong() throws NumberFormatException, IOException
    {
      return Long.parseLong(nextToken());
    }

    double nextDouble() throws NumberFormatException, IOException
    {
      return Double.parseDouble(nextToken());
    }

    String nextLine() throws IOException
    {
      tokenizer = null;
      return reader.readLine();
    }
  }
}
