
def solve():
    N = int(raw_input())
    v = [int(_) for _ in raw_input().split()]
    v.sort()
    new_mat = v[0]
    for i in range(1, N):
        new_mat = (new_mat + v[i]) / 2.0
    print new_mat

if __name__ == '__main__':
    solve()
