Given an array, $A$, having $N$ integers $A_1,A_2,...,A_N$.Two elements of the array $A_i$ and $A_j$ are called similar iff $A_i = A_j+1$ or $A_j = A_i + 1$ .
Also, the similarity follows transitivity. If $A_i$ and $A_j$ are similar and $A_j$ and $A_k$ are similar, then $A_i$ and $A_k$ are also similar. 
Note: $i$, $j$, and $k$ are all distinct.

You need to find number of pairs of indices $(i,j)$ such that $i<j$ and $A_i$ is similar to $A_j$.

Input

The first line contains a single integer $N$ denoting number of elements in the array.
The second line contains $N$ space separated integers where $i^{th}$ elements indicate$A_i$.

Output

Output the number of pairs of indices $(i,j)$ such that $i<j$ and $A_i$ is similar to $A_j$ in a single line.

Constraints

$1 \le N \le 10^6\\ 10^{-9} \le A_i \le 10^9$