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

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