import heapq

N = int(input())
V = []
for v in map(int, input().split()):
    heapq.heappush(V, v)

while len(V) > 2:
    a, b = heapq.heappop(V), heapq.heappop(V)
    heapq.heappush(V, (a + b) // 2)
print((heapq.heappop(V) + heapq.heappop(V)) / 2)
