num=int(input())
list1=[]
lst=input().split(" ")
for i in range(num):
    lst[i]=int(lst[i])
    list1.append([i+1,lst[i]])
dict1=dict(list1)
dict1=sorted(dict1.items(),key=lambda x: x[1])
m=1
for i in dict1:
    if m<=9:
        print(i[0],end=" ")
        m+=1
    else:
        print(i[0])
sum=0
lst=sorted(lst)
num-=1
for j in lst:
    sum+=j*num
    num-=1
ans=sum/len(lst)
print('%.2f' % ans)