#include <iostream>
#include <cmath>
using namespace std;
typedef long double ld;
ld p[100010],q[100010],a[100010];
bool ch(int n,ld val){
    ld res = -val;
    for(int i=0;i<n;i++) res += p[i]*(1 - q[i])/(1 - q[i]*val);
    if(res>0) return false;
    return true;
}

int main(){
    cout.precision(20);
    int i,n; cin >> n;
    for(i=0;i<n;i++) cin >> p[i];
    for(i=0;i<n;i++) cin >> q[i];
    for(i=0;i<n;i++) cin >> a[i];
    ld l = 0,r = 0.9999999999999;
    for(i=0;i<=200;i++){
        ld mid = (l + r)/2;
        if(ch(n,mid)) r = mid;
        else l = mid;
    }
    ld ans = 0;
    for(i=0;i<n;i++){
        ans += a[i]*log((1 - q[i])/(1 - q[i]*r));
    }
    cout << ans << endl;
}