import csv 

import math
with open('data.csv', newline='')as f :
    reader=csv.reader(f)
    file_data=list(reader)
data=file_data[0]    

def mean(data):
    n=len(data)
    total=0
    for x in data:
        total+=int(x)
    mean=total/n
    return mean

squared_list=[]      
for number in data:
    a=int(number)-mean(data)
    a=a**2
    squared_list.append(a)
sum=0
for i in squared_list:
    sum=sum+i
result=sum/(len(data)-1)        
st=math.sqrt(result)
print(st)