'''
Objective 
In the previous challenge, we calculated a mean. In this challenge, we practice calculating a weighted mean. Check out the Tutorial tab for learning materials and an instructional video!

Task 
Given an array, , of  integers and an array, , representing the respective weights of 's elements, calculate and print the weighted mean of 's elements. Your answer should be rounded to a scale of  decimal place (i.e.,  format).

Input Format

The first line contains an integer, , denoting the number of elements in arrays  and . 
The second line contains  space-separated integers describing the respective elements of array . 
The third line contains  space-separated integers describing the respective elements of array .

Constraints

, where  is the  element of array .
, where  is the  element of array .
Output Format

Print the weighted mean on a new line. Your answer should be rounded to a scale of decimal place (i.e.,  format).

Sample Input

5
10 40 30 50 20
1 2 3 4 5
Sample Output

32.0
Explanation

We use the following formula to calculate the weighted mean:

And then print our result to a scale of  decimal place () on a new line.
'''

# Enter your code here. Read input from STDIN. Print output to STDOUT

# import numpy as np

n = int(input())
x = list(map(int, input().split()))
y = list(map(int, input().split()))


# print(round(np.average(x, weights = y), 1))

print(round(sum(map(lambda a: a[0] * a[1], zip(x,y)))/sum(y), 1))

