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;
import java.util.TreeSet;

public class B {

	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		int n = sc.nextInt();
		int[] a = new int[n];
		TreeSet<Integer> set = new TreeSet<>();
		for (int i = 0; i < a.length; i++) {
			a[i] = sc.nextInt();
			set.add(a[i]);
		}
		int idx = 1;
		HashMap<Integer, Integer> mp = new HashMap<>();
		for (int i : set) {
			mp.put(i, idx++);
		}
		FenwickTree num = new FenwickTree(idx);
		FenwickTree sum = new FenwickTree(idx);
		BigInteger b = new BigInteger("0");
		Integer ind = 0, tmp = 0;
		for (int i = 0; i < a.length; i++) {
			tmp = set.floor(a[i] - 2);
			if (tmp != null) {
				ind = mp.get(tmp);
				b = b.add(BigInteger.valueOf(num.rsq(ind) * a[i] - sum.rsq(ind)));
			}
			tmp = set.ceiling(a[i] + 2);
			if (tmp != null) {
				ind = mp.get(tmp);
				b = b.add(BigInteger.valueOf(num.rsq(ind, idx) * a[i] - sum.rsq(ind, idx)));
			}
			ind = mp.get(a[i]);
			num.point_update(ind, 1);
			sum.point_update(ind, a[i]);
		}
		out.println(b);
		out.flush();
		out.close();
	}

	static class FenwickTree { // one-based DS

		int n;
		long[] ft;

		FenwickTree(int size) {
			n = size;
			ft = new long[n + 1];
		}

		long rsq(int b) // O(log n)
		{
			long sum = 0;
			while (b > 0) {
				sum += ft[b];
				b -= b & -b;
			} 
			return sum;
		}

		long rsq(int a, int b) {
			return rsq(b) - rsq(a - 1);
		}

		void point_update(int k, int val) // O(log n), update = increment
		{
			while (k <= n) {
				ft[k] += val;
				k += k & -k;
			} 
		}

	}

	static class Scanner {
		BufferedReader bf;
		StringTokenizer st;

		public Scanner(InputStream i) {
			bf = new BufferedReader(new InputStreamReader(i));

		}

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

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

		public double nextDouble() throws IOException {
			String x = next();
			StringBuilder sb = new StringBuilder("0");
			double res = 0, f = 1;
			boolean dec = false, neg = false;
			int start = 0;
			if (x.charAt(0) == '-') {
				neg = true;
				start++;
			}
			for (int i = start; i < x.length(); i++)
				if (x.charAt(i) == '.') {
					res = Long.parseLong(sb.toString());
					sb = new StringBuilder("0");
					dec = true;
				} else {
					sb.append(x.charAt(i));
					if (dec)
						f *= 10;
				}
			res += Long.parseLong(sb.toString()) / f;
			return res * (neg ? -1 : 1);
		}

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