import sys

n = int(input())
v = [float(x) for x in input().split()]

for _ in range(n):
    if len(v) == 1:
        break
    smallest = 1000000000000000000000000000000
    smallest_x = 0
    smallest_y = 0
    for x in range(len(v)):
        for y in range(x + 1, len(v), 1):
            if smallest > abs(v[x] - v[y]):
                smallest = abs(v[x] - v[y])
                smallest_x = x
                smallest_y = y
    y = v.pop(smallest_y)
    x = v.pop(smallest_x)
    v.append((y + x) / 2)

if len(v) > 1:
    print(v[0] + v[1] / 2)
    sys.exit()
print(v[0])