from math import sqrt
from numpy import array, mean 
N=int(input())
x=array([*map(int, input().split())])
M=int(input())
mae=0
ave=mean(x)
for i in x:
    mae+=pow(ave-i,2)/N
print(0 if sqrt(mae) == 0 else int((x[M-1]-ave)*10/sqrt(mae)+50))