All Tracks Data Structures Arrays 1-D Problem

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

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