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ZOJ Problem Set - 2091
Mean of Subsequence

Time Limit: 2 Seconds      Memory Limit: 65536 KB

Given N numbers in a line, we can determine a continuous subsequence by giving its start position and its length.

PMH and Roy played a game the other day. Roy gives the start position first, then PMH gives the length. Roy wants the mean of the subsequence as large as possible, while PMH wants it as small as possible.

You are to calculate the best result Roy can get, assuming PMH is very clever.


Input

There are multiple testcases.

Each testcase begins with a line containing N only.

The following line contains N numbers, separated by spaces.


Output

For each testcase, you are to print the best mean of subsequece Roy can get, precise to 6 digit after decimal point.


Sample Input

10
2 10 4 6 5 10 10 2 3 2


Sample Output

5.777778



Author: SHI, Xiaohan
Source: ZOJ Monthly, March 2004
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