You are given a sequence $a = (a_1, \dots, a_N)$ of length $N$ consisting of integers between $1$ and $N$.

Find the number of pairs of integers $i, j$ that satisfy all of the following conditions:

-   $1 \leq i \lt j \leq N$
-   $\min(a_i, a_j) = i$
-   $\max(a_i, a_j) = j$

Input is given from Standard Input in the following format:

```
$N$
$a_1$ $\ldots$ $a_N$
```

Print the answer.

-   $2 \leq N \leq 5 \times 10^5$
-   $1 \leq a_i \leq N \, (1 \leq i \leq N)$
-   All values in input are integers.

2

(i,j)=(1,4),(2,3) satisfy the conditions.