A set is an unordered collection of elements without duplicate entries.

When printed, iterated or converted into a sequence, its elements will appear in an arbitrary order.

Example

print set()
set([])

print set('HackerRank')
set(['a', 'c', 'e', 'H', 'k', 'n', 'r', 'R'])

print set([1,2,1,2,3,4,5,6,0,9,12,22,3])
set([0, 1, 2, 3, 4, 5, 6, 9, 12, 22])

print set((1,2,3,4,5,5))
set([1, 2, 3, 4, 5])

print set(set(['H','a','c','k','e','r','r','a','n','k']))
set(['a', 'c', 'r', 'e', 'H', 'k', 'n'])

print set({'Hacker' : 'DOSHI', 'Rank' : 616 })
set(['Hacker', 'Rank'])

print set(enumerate(['H','a','c','k','e','r','r','a','n','k']))
set([(6, 'r'), (7, 'a'), (3, 'k'), (4, 'e'), (5, 'r'), (9, 'k'), (2, 'c'), (0, 'H'), (1, 'a'), (8, 'n')])

Basically, sets are used for membership testing and eliminating duplicate entries.

Task

Now, let's use our knowledge of sets and help Mickey.

Ms. Gabriel Williams is a botany professor at District College. One day, she asked her student Mickey to compute the average of all the plants with distinct heights in her greenhouse.

Formula used: $\textit{Average}=\dfrac{\textit{Sum ofDistinct Heights}}{\textit{Total Number of distinct Heights}}$

Function Description

Complete the average function in the editor below.

average has the following parameters:

int arr: an array of integers

Returns

float: the resulting float value rounded to 3 places after the decimal

Input Format

The first line contains the integer, $N$, the size of $\textbf{arr}$.

The second line contains the $N$ space-separated integers, $arr\left[i\right]$.

Constraints

$0<N\leq100$

Sample Input
STDIN Function
----- --------
10 arr[] size N = 10
161 182 161 154 176 170 167 171 170 174 arr = [161, 181, ..., 174]

Sample Output
169.375

Explanation

Here, set$([154,161,167,170,171,174,176,182])$ is the set containing the distinct heights. Using the sum() and len() functions, we can compute the average.

$\textit{Average}=\dfrac{1355}{8}=169.375$

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