def m():
    N = int(input())
    V = [int(i) for i in input().split()]
    while len(V) > 1:
        min_v = 10000
        min_i = 0
        for i, v in enumerate(V[:-1]):
            if min_v > V[i] + V[i+1]:
                min_v = V[i] + V[i+1]
                min_i = i
        V[min_i] = (V[min_i] + V[min_i+1]) / 2
        V.pop(min_i+1)
    print(V[0])

m()
