Problem Statement

There are $N$ rabbits, numbered $1$ through $N$.

The $i$-th ($1≤i≤N$) rabbit likes rabbit $a_i$. Note that no rabbit can like itself, that is, $a_i≠i$.

For a pair of rabbits $i$ and $j$ ($i＜j$), we call the pair ($i，j$) a friendly pair if the following condition is met.

• Rabbit $i$ likes rabbit $j$ and rabbit $j$ likes rabbit $i$.

Calculate the number of the friendly pairs.

Constraints

• $2≤N≤10^5$
• $1≤a_i≤N$
• $a_i≠i$

Input

The input is given from Standard Input in the following format:

$N$ $a_1$ $a_2$ $...$ $a_N$

Output

Print the number of the friendly pairs.

Sample Input 1

4
2 1 4 3

Sample Output 1

2

There are two friendly pairs: $(1，2)$ and $(3，4)$.

Sample Input 2

3
2 3 1

Sample Output 2

0

There are no friendly pairs.

Sample Input 3

5
5 5 5 5 1

Sample Output 3

1

There is one friendly pair: $(1，5)$.