#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

int N;
vector<double> p, q;

void solve(){
    rep(i, N)p[i] *= 0.001;
    rep(i, N)q[i] *= 0.01;
    int cnt = 0;

    priority_queue<pair<double, int> > Q;
    rep(i, N)Q.push(mp(p[i] * q[i], i));

    double ans = 0;
    rep(iter_, 10000000){
        double x;
        int k;
        tie(x, k) = Q.top();
        Q.pop();
        Q.push(mp(x*(1 - q[k]), k));
        ans += x * ++cnt;
    }

    cout << setprecision(20) << ans << endl;
}

int main(){
    while(cin >> N){
        p.resize(N);
        q.resize(N);
        rep(i, N)scanf("%lf", &p[i]);
        rep(i, N)scanf("%lf", &q[i]);
        solve();
    }
}