Given an array $A$ of length $N$. Find the number of ordered pairs $(i, j)$ which satisfy the given condition

• $(A[i] - A[j]) / (i - j) = 1$
• $A[i] - A[j]$ should be divisible by $i-j$
• $i \neq j$

Input format

• The first line contains an integer $N$.
• The second line of each test case contains $N$ space-separated integers, denoting the elements of array $A$.

Output format

Print the number of ordered pairs (i, j) which satisfy the above condition in a new line.

Constraints

$1 \le N \le 5 \times 10 ^ 5 \\ 1 \le A[i] \le 10^6$