Seeing the Shape of Exam Scores

Ashgrove Analytics writes the end-of-term results pack for Calder Sixth Form. Each page shows this year's scores grouped into bands, and below the picture sits a one-line caption giving the spread. The drawing code is already in place and no part of the picture is checked — the caption is the only thing graded.

Task: Print the standard deviation of the scores: one number saying how far a typical score sits from the average. Treat the scores you are given as the whole population, not as a sample standing in for some larger group. That choice changes the answer.

Input

The first line holds an integer n, the number of scores. Each of the next n lines holds one score, a number from 0 to 100. n is at least 1.

Output

One line: the standard deviation with exactly 2 digits after the decimal point. A spread of five and a half prints as 5.50.

Example:

Input:
4
60
70
80
90

Output:
11.18