from heapq import heappush, heappop N = int(input()) vLst = list(map(int, input().split())) v = [] for i in range(N): heappush(v, vLst[i]) ans = 0 for i in range(N - 1): tmp1 = heappop(v) tmp2 = heappop(v) ans = float((tmp1 + tmp2) / 2) heappush(v, ans) print(v[0])
