def alchemist(n,v):
    _v = sorted(v)
    tmp = _v[0]

    for i in range(1,n):
        tmp = (tmp + _v[i])/2

    return tmp
if __name__ == '__main__':
    n = int(raw_input())
    v = map(float,raw_input().split())

    print alchemist(n,v)