n=int(input()) 
lst=list(map(int,input().split())) 
#print(lst) 
a=[] 

for i in range(n): 
	if i==0: 
		#print(lst[i]) 
		a.append(lst[i]) 
	else: 
		#print(lst[i]) 
		a.append((a[-1]+lst[i])/2)   
print(a[-1])
