# Morning exercises

Very easy

Execution time limit is 1 second

Runtime memory usage limit is 128 megabytes

In the morning, many students do their exercises. According to established tradition, the students dance in the branded T-shirts. During the first three days of the camp, schoolchildren and teachers noticed that a couple who dances in identical T-shirts looks more aesthetically better. Therefore before the exercises, they decided first to put pairs of children in identical T-shirts, and then the remaining ones. The excellent student Seryozha wanted to know what the largest number of aesthetic pairs can be formed from everyone who came to morning exercises.

## Input

Sequence of n (n ≤ `10^6`

) positive integers, giving the colour of a T-shirt (the colour is a number from 0 to 9).

## Output

Print the number of aesthetic pairs that can be made up.

## Examples

Input #1

Answer #1

Submissions 3K

Acceptance rate 46%