#include <iostream>
#include <stdio.h>
#include <cmath>
using namespace std;

struct pt{
	double x,y;
};

double a[233], b[233], c[233], d[233];
int n;

void initX(double *x){
	for(int i = 1; i <= n; i++){
		scanf("%lf", &x[i]);
	}
}

bool init(){
	scanf("%d", &n);
	if(!n) return 0;
	a[0] = b[0] = c[0] = d[0] = 0;
	initX(a);
	initX(b);
	initX(c);
	initX(d);
	a[n+1] = b[n+1] = c[n+1] = d[n+1] = 1;
	return 1;
}

double getArea(pt& p1, pt& p2, pt& p3){
	return 0.5*abs(p1.x*(p2.y-p3.y)+p2.x*(p3.y-p1.y)+p3.x*(p1.y-p2.y));
}

pt getInt(int i, int j){
	pt p;
	double fm = 1-(b[i]-a[i])*(d[j]-c[j]);
	p.x = (c[j]*b[i]+(1-c[j])*a[i])/fm;
	p.y = ((1-a[i])*c[j]+a[i]*d[j])/fm;
	return p;
}

double getArea(int i, int j){
	pt p1 = getInt(i,j), p2 = getInt(i,j+1), p3 = getInt(i+1,j+1), p4 = getInt(i+1,j);
	return getArea(p1,p2,p3)+getArea(p3,p4,p1);
}

double getMax(){
	double mx = 0.0;
	for(int i = 0; i <= n; i++){
		for(int j = 0; j <= n; j++){
			double tmp = getArea(i,j);
			if(tmp > mx) mx = tmp;
		}
	}
	return mx;
}

int main() {
	while(init()){
		printf("%.6lf\n", getMax());
	}
	return 0;
}