package main

import (
	"bufio"
	"container/heap"
	"fmt"
	"os"
	"sort"
	"strconv"
)

func out(x ...interface{}) {
	fmt.Println(x...)
}

var sc = bufio.NewScanner(os.Stdin)

func getInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func getInts(N int) []int {
	ret := make([]int, N)
	for i := 0; i < N; i++ {
		ret[i] = getInt()
	}
	return ret
}

func getString() string {
	sc.Scan()
	return sc.Text()
}

// min, max, asub, absなど基本関数
func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func asub(a, b int) int {
	if a > b {
		return a - b
	}
	return b - a
}

func abs(a int) int {
	if a >= 0 {
		return a
	}
	return -a
}

func lowerBound(a []int, x int) int {
	idx := sort.Search(len(a), func(i int) bool {
		return a[i] >= x
	})
	return idx
}

func upperBound(a []int, x int) int {
	idx := sort.Search(len(a), func(i int) bool {
		return a[i] > x
	})
	return idx
}

type pqi struct {
	p float64
	n int
}

type priorityQueue []pqi

func (pq priorityQueue) Len() int            { return len(pq) }
func (pq priorityQueue) Swap(i, j int)       { pq[i], pq[j] = pq[j], pq[i] }
func (pq priorityQueue) Less(i, j int) bool  { return pq[i].p > pq[j].p }
func (pq *priorityQueue) Push(x interface{}) { *pq = append(*pq, x.(pqi)) }
func (pq *priorityQueue) Pop() interface{} {
	x := (*pq)[len(*pq)-1]
	*pq = (*pq)[0 : len(*pq)-1]
	return x
}

func main() {
	sc.Split(bufio.ScanWords)
	sc.Buffer([]byte{}, 1000000)
	n := getInt()
	p := getInts(n)
	q := getInts(n)

	pq := priorityQueue{}
	for i := 0; i < n; i++ {
		x := float64(p[i]*q[i]) / 100000.0
		heap.Push(&pq, pqi{x, i})
	}

	ret := 0.0
	for i := 0; i < 1000000; i++ {
		if len(pq) != 0 {
			r := heap.Pop(&pq).(pqi)
			ret += float64(i+1) * r.p
			x := r.p * (1 - float64(q[r.n])/100.0)
			heap.Push(&pq, pqi{x, r.n})
		}
	}
	out(ret)
}