n = int(raw_input())
v = map(int, raw_input().split())
new_v = sorted(v)
pre_v = new_v[0]
out = 0.0
for i in range(1,n):
    out = (pre_v + float(new_v[i]))/2.0
    pre_v = (pre_v + float(new_v[i]))/2.0
print(out)