Problem Statement

You have $N$ socks. The color of the $i$-th sock is $A_i$.

You want to perform the following operation as many times as possible. How many times can it be performed at most?

• Choose two same-colored socks that are not paired yet, and pair them.

Constraints

• $1\\leq N \\leq 5\\times 10^5$
• $1\\leq A_i \\leq 10^9$
• All values in the input are integers.

Input

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

$N$ $A_1$ $A_2$ $\\dots$ $A_N$

Output

Print an integer representing the answer.

Sample Input 1

6
4 1 7 4 1 4

Sample Output 1

2

You can do the operation twice as follows.

• Choose two socks with the color $1$ and pair them.
• Choose two socks with the color $4$ and pair them.

Then, you will be left with one sock with the color $4$ and another with the color $7$, so you can no longer do the operation. There is no way to do the operation three or more times, so you should print $2$.

Sample Input 2

1
158260522

Sample Output 2

0

Sample Input 3

10
295 2 29 295 29 2 29 295 2 29

Sample Output 3

4