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.util.*;
import java.io.*;
import java.math.BigInteger; 
public class lp{ 
static PrintWriter out = new PrintWriter(System.out);
static BigInteger ddd(BigInteger num1 ,BigInteger num2){

          return num1.add(num2);    
}
static void solve() {

int n = ni();
long a[] = al(n);
int l[] = new int[n];
int r[] = new int[n];
long p[] = new long[n];

for(int i=0;i<n;i++)
{
    p[i] = a[i];
    if(i>0)
    p[i] = p[i] + p[i-1] ;
}

HashMap<Long,Integer> hm = new HashMap();

for(int i=n-1;i>=0;i--)
{
    if(i==(n-1))
      hm.put(a[i],hm.getOrDefault(a[i],0)+1);
    else
     {
         l[i] = hm.getOrDefault(a[i]-1,0);
         r[i] = hm.getOrDefault(a[i]+1,0);
        hm.put(a[i],hm.getOrDefault(a[i],0)+1);
     }
}
BigInteger ans =  BigInteger.valueOf(0);
for(int i=0;i<(n-1);i++)
{
    long xx = p[n-1]-p[i] - a[i]*(n-1-i) + l[i] -r[i] ;
    ans = ddd(ans ,BigInteger.valueOf(xx)) ;
}
pn(ans);
   out.flush();
}
public static void main(String[] args) throws Exception{


// use this block when you need more recursion depth
new Thread(null, null, "Name", 999999999) {
            public void run() {
                try {
                    solve();
                } catch(Exception e) {
                    e.printStackTrace();
                    System.exit(1);
                }
            }
        }.start();  
} 
static int[] ai(int n)  // it will give in array of size n
{
    int a[] = new int[n];
    for(int i=0;i<n;i++)
        a[i] = ni();
    return a;
}
static long[] al(int n)  // it will give in array of size n
{
    long a[] = new long[n];
    for(int i=0;i<n;i++)
        a[i] = nl();
    return a;
}
 
static void p(Object o)
{
   out.print(o);
}
static void pn(Object o)
{
    out.println(o);
}
static int abs(int x)
{
    return x>0 ? x : -x;
}
static long gcd(long a,long b)
{
       if(a==0)
          return b;
       if(b==0)
          return a;
       if(b%a==0)
          return a;
          return gcd(b%a,a);
}
static int count_set(int n)
{
   int c=0;
while(n>0)
{
   if(n%2==1)
     c++;
     n=n/2;
}
   return c;
}
static void subtract_1(char s[]) // it will subtract 1 from the given number.  number should be positive
{
      if(s[0]=='0') // number is zero
          return;
     int n = s.length,i=n-1;
     while(s[i]=='0')
       i--;
     s[i] = (char)((int)(s[i]-'0') + 47);
   
     for(int j=i+1;j<n;j++)
         s[j]='9';
}
static long pow(long a,long b,long md)
{ 
    long ans=1;
    while(b>0)
    {
         if(b%2==1)
           ans = (ans*a)%md;
           a = (a*a)%md;
           b = b/2;
    }
   return ans;
}
static long min(long a,long b){
 
     return a<b ? a : b;
}
static long max(long a,long b){
     return a>b ? a : b;
}
static boolean pal(String s)
{
   int n = s.length(),i1=0,i2=n-1;
 
     while(i1<i2)
     {
        if(s.charAt(i1)!=s.charAt(i2))
             return false;
             i1++; i2--;
     }
       return true;
}
static String rev(String r)
{
    String s = "";
    int i= r.length()-1;
 
    while(i>=0)
    {
        s=s+r.charAt(i);
        i--;   
    }
       return s;
}
static FastReader sc=new FastReader(); 
 
      static int ni(){
                 int x = sc.nextInt();
                 return(x);
        }
      static long nl(){
              long x = sc.nextLong();
              return(x);
         }
      static String n(){
                 String str = sc.next();
                     return(str);
       }
     static String ns(){
                 String str = sc.nextLine();
                   return(str);
      }
     static double nd(){
               double d = sc.nextDouble();
                 return(d);
       }
  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; 
        } 
    } 
}