A positive integer $N$ and a sequence $A = [A_1, A_2, \cdots, A_{2N}]$ of length $2N$ are given. Find the number of integer pairs $(i, j)$ that satisfy the following conditions.

• $1 \leq i \leq N$.
• $1 \leq j \leq N$.
• $A_i + A_j = A_{i + j}$.

The input is given in the following format.

$N$ $A_1 \ A_2 \ \cdots \ A_{2N}$

Print the answer of the problem on the first line.

• $1 \leq N \leq 2 \ 000$.
• $1 \leq A_i \leq 1 \ 000 \ 000 \ 000$ ($1 \leq i \leq 2N$).