In Statistics, Variance is a measure of how values vary from the mean. The Variance of a series of numbers can be calculated with the following formula

• σ2 is the variance of a series
• n is the number of elements in the series
• xi represents each number in the series
• µ is the mean of series

The variance of the series {1, 2, 3, 4, 5, 6} then can be calculated, like this:
  µ = (1 + 2 + 3 + 4 + 5 + 6) / 6 = 3.5
S = (1 - 3.5)2 + (2 - 3.5)2 + (3 - 3.5)2 + (4 - 3.5)2 + (5 - 3.5)2 + (6 - 3.5)2
    = (-2.5)2 + (-1.5)2 + (-0.5)2 + (0.5)2 + (1.5)2 + (2.5)2
    = 17.5
 σ2 = (1 / n) * S = (1 / 6) * 17.5
 σ2 = 2.9167


Input specification
You will first be given a number (n) which shows the number of numbers in the following line. The following line contains n integer numbers (xi) where each of the numbers is 1 ≤ x_i ≤ 3000 and 1 ≤ n ≤ 5000.

Output specification
Show one float number that represent the variance of the given series.