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You have final scores of an examination for `n` students. Calculate standard deviation of the scores `s _{1}`,

The variance α^{2} is defined by

α^{2} = (∑^{n}_{i=1}(s_{i} - m)^{2})/n

where `m` is an average of `s _{i}`.
The standard deviation of the scores is the square root of their variance.

The input consists of multiple datasets. Each dataset is given in the following format:

ns_{1}s_{2}...s_{n}

The input ends with single zero for `n`.

For each dataset, print the standard deviation in a line. The output should not contain an absolute error greater than 10^{-4}.

`n`≤ 1000- 0 ≤
`s`≤ 100_{i}

5 70 80 100 90 20 3 80 80 80 0

27.85677655 0.00000000