n = int(input())
students = list(map(int, input().split()))
m = int(input())

ave = sum(students) / n
var = 0
for student in students:
    var += ((student - ave) ** 2)

std = (var / n) ** 0.5

ans = []

for student in students:
    ans.append(int(((student - ave) / std) * 10 + 50))

print(ans[m-1])