Unique Mean Calculation

Given an array of integers, you are required to compute the arithmetic mean of the unique elements in the array. The process involves:

• Extracting the unique elements from the array.
• Sorting these unique elements in non-decreasing order.
• Calculating the mean (average) of the sorted unique elements.

The result should be printed as a floating point number. For example, if the array is [1, 2, 2, 3, 3, 3, 4, 4, 4, 4], the unique elements are [1, 2, 3, 4] whose mean is \(\frac{1+2+3+4}{4} = 2.5\).

inputFormat

The input is read from stdin and consists of two lines:

1. The first line contains an integer \(N\) representing the number of elements in the array.
2. The second line contains \(N\) space-separated integers.

outputFormat

Output the mean of the unique elements as a floating point number to stdout. The answer should be printed with one digit after the decimal point.

## sample

10
1 2 2 3 3 3 4 4 4 4

2.5

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