
N = int(input())
v_list = list(map(int, input().split()))

v_list_sorted = sorted(v_list)

sum = 0
tmp_min = 0

if N == 1:
    print(v_list[0])
    exit(0)

for i in range(0, N - 1):
    if i == 0:
        merged = (v_list_sorted[i] + v_list_sorted[i + 1]) / 2
        tmp_min = merged
        sum = merged
    else:
        sum = (tmp_min + v_list_sorted[i + 1]) / 2
print(sum)
