The Volatility Number

Harborlight Capital publishes a volatility figure for every fund it tracks: how far a typical day's return sits from that fund's own average return. The desk only ever holds a window of recent days, never the fund's entire history, so it quotes the sample standard deviation — the version intended for a handful of observations drawn from a much larger population, rather than the version for a complete population. The two are not the same number, and picking the wrong one quietly understates the risk.

Task: Print the sample standard deviation of the daily returns.

Input

The first line holds one integer n, how many daily returns follow; n is at least 2. Each of the next n lines holds one return as a plain number. A return may carry a decimal point and may be negative.

Output

One line holding the sample standard deviation with exactly two digits after the decimal point.

Example:

Input:
4
2
4
4
6

Output:
1.63