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.math.BigInteger;
import java.util.Map.Entry;
import java.util.StringTokenizer;
import java.util.TreeMap;



public class D {
static BigInteger ans;
	public static void main(String[] args) throws IOException {
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		TreeMap<Long,Long> map=new TreeMap();
		long s=0;
		ans=BigInteger.ZERO;
		
		for(int i=1;i<=n;i++)
		{
			long x=sc.nextInt();
			add(x*(i-1)-s);
			if(map.containsKey(x-1))
			{	
				add(map.get(x-1)*(x-1));
				subtract(map.get(x-1)*x);
			}	
			if(map.containsKey(x+1))
			{	
				add(map.get(x+1)*(x+1));
				subtract(map.get(x+1)*x);
			}
			if(map.containsKey(x))
			{	
				add(map.get(x)*(x));
				subtract(map.get(x)*x);
			}
			
			
			s+=x;
			if(map.containsKey(x))
			
				map.put(x, map.get(x)+1);
			
			else
				map.put(x, 1L);
		}
		System.out.println(ans);
	}
	public static void add(long x)
	{
		ans=ans.add(new BigInteger(x+""));
	}
	public static void subtract(long x)
	{
		ans=ans.subtract(new BigInteger(x+""));
	}
	
	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
		{
			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 boolean ready() throws IOException {return br.ready();}


	}
	static class pair 
	{
		long sum;
		int count ;
		public pair(int x,long y)
		{
			count=x;sum=y;
		}
		public String toString() {
			return count+" "+sum; 
		}
	}
}
