std.py

# Enter your code here. Read input from STDIN. Print output to STDOUT
import math

def find_mean(arr):
    return sum(arr) / len(arr)

def find_std(arr, mean):
    variances = []
    for x in arr:
        variances.append(abs(x - mean) ** 2)
    return math.sqrt(sum(variances) / len(variances))


if __name__ == '__main__':
    length_array = input()
    array = [int(x) for x in input().split(' ')]
    mean = find_mean(array)
    variances = find_std(array, mean)
    print(variances)