n = int(input())
i = list(map(int, input().split()))
m = n
n -= 1
i.sort()

if i.count(i[0])==m:
    ans = i[0]
else:
    for j in range(n):
        if(j<n-1):
            if(i.count(i[0])>1):
                tmp = i[j]
            else:
                tmp = (i[j]+i[j+1])/2
            i.append(tmp)
            del i[0:2]
        i.sort()
    ans = (i[0]+i[1])/2

print(ans)
