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. 
//189301019.akshay
import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.util.Scanner; 
import java.util.Random;
import java.util.Arrays;
import java.util.StringTokenizer; 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Collections;
import java.math.BigInteger;
public class D 
{ 
    public static void main(String[] args) 
	{ 
		FastReader sc=new FastReader(); 
		StringBuffer ans=new StringBuffer();
		int test=1;
		while(test-->0)
		{
			BigInteger sum=new BigInteger("0");
			int n=sc.nextInt();
			long arr[]=new long[n];
			long dif[]=new long[n];
			long pre[]=new long[n];
			long legit[]=new long[n];
			for(int i=0;i<n;i++) {
				arr[i]=sc.nextLong();
				pre[i]=(i>0?pre[i-1]:0)+arr[i];
			}
			HashMap<Long,Long> map=new HashMap<>();
//			long sum =0l;
			for(int i=n-1;i>=0;i--) {
				long x =map.getOrDefault(arr[i]+1, 0l);
				long y =map.getOrDefault(arr[i]-1, 0l);
				long z =map.getOrDefault(arr[i], 0l);
				legit[i] =n-(i+1) -x -y -z;
				dif[i] =(x*(arr[i]+1l))+(y*(arr[i]-1l))+(z*(arr[i]));
		
				long total =pre[n-1] -pre[i] -dif[i];
				total-=(legit[i]*arr[i]);
				sum=sum.add(BigInteger.valueOf(total));
//				sum+=total;
				map.put(arr[i],map.getOrDefault(arr[i], 0l)+1l);
			}
			
			ans.append(sum+"\n");
			
		
		}
		
	    System.out.print(ans);
	} 
    
    static final Random random=new Random();
    
	static void ruffleSort(int[] a) {
		int n=a.length;//shuffle, then sort 
		for (int i=0; i<n; i++) {
			int oi=random.nextInt(n), temp=a[oi];
			a[oi]=a[i]; a[i]=temp;
		}
		Arrays.sort(a);
	}
	
	static void ruffleSort(long[] a) {
		int n=a.length;//shuffle, then sort 
		for (int i=0; i<n; i++) {
			int oi=random.nextInt(n);
			long temp=a[oi];
			a[oi]=a[i]; a[i]=temp;
		}
		Arrays.sort(a);
	}
	
	static class FastReader 
	{ 
		BufferedReader br; 
		StringTokenizer st; 

		public FastReader() 
		{ 
			br = new BufferedReader(new
					InputStreamReader(System.in)); 
		} 

		String next() 
		{ 
			while (st == null || !st.hasMoreElements()) 
			{ 
				try
				{ 
					st = new StringTokenizer(br.readLine()); 
				} 
				catch (IOException e) 
				{ 
					e.printStackTrace(); 
				} 
			} 
			return st.nextToken(); 
		} 

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

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

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

		String nextLine() 
		{ 
			String str = ""; 
			try
			{ 
				str = br.readLine(); 
			} 
			catch (IOException e) 
			{ 
				e.printStackTrace(); 
			} 
			return str; 
		} 
	} 


} 
