Standard Deviation of Delivery Times

Whetcode Delivery prints "about 20 minutes" on the lid of every box, and support keeps taking calls from customers who waited noticeably longer. The ops lead is not arguing about the average - she wants to know how far from it a typical delivery actually lands, in minutes, so the promise on the lid can be rewritten as a window instead of a single point.

She reviews one route per night, and every route has a different number of drops, so the figure has to be produced from whatever last night's run recorded. Whatever arrives is the complete run for that route, not a sample of a bigger one.

Task: Print the population standard deviation of the delivery times, rounded to 2 decimals.

Input

One line holding the door-to-door times in whole minutes, separated by single spaces, in the order the drops were made. There are at least two of them.

Output

One line holding the population standard deviation, rounded to 2 decimals and printed the way Python prints a float - 4.9, never 4.90.

Example:

Input:
10 12 23 23 16 23 21 16

Output:
4.9