N = int(input())
v_n = sorted(map(int, input().split()))

if N % 2:
    v_last = v_n[N-1]
else:
    v_last = None

while len(v_n) > 1:
    w_n = [0] * (len(v_n)//2)
    for i in range(len(w_n)):
        j, k = i*2, i*2+1
        w_n[i] = (v_n[j] + v_n[k]) / 2
    v_n = w_n

if v_last is None:
    ans = v_n[0]
else:
    ans = (v_n[0]+v_last) / 2
print(ans)
