/**************** Geometrical Library ****************/

#include<cmath>
#include<vector>
#include<algorithm>

#define	EPS	1e-9

enum {CCW=1,CW=-1,ON=0};

#define	pb	push_back

using namespace std;

class Point{
public:
	double x,y;
	Point(){}
	Point(double xx,double yy):x(xx),y(yy){}
};

class Line:public vector<Point>{
public:
	Line(){}
	Line(const Point &a,const Point &b){
		pb(a),pb(b);
	}
};

class Segment:public Line{
public:
	Segment(){}
	Segment(const Point &a,const Point &b):Line(a,b){}
};

Point &operator +=(Point &a,const Point &b){
	a.x+=b.x,a.y+=b.y;
	return a;
}

Point &operator -=(Point &a,const Point &b){
	a.x-=b.x,a.y-=b.y;
	return a;
}

Point &operator *=(Point &a,double c){
	a.x*=c,a.y*=c;
	return a;
}

Point &operator /=(Point &a,double c){
	a.x/=c,a.y/=c;
	return a;
}

Point operator +(const Point &a,const Point &b){
	Point c=a;
	return c+=b;
}

Point operator -(const Point &a,const Point &b){
	Point c=a;
	return c-=b;
}

Point operator *(double c,const Point &a){
	Point b=a;
	return b*=c;
}

Point operator /(const Point &a,double c){
	Point b=a;
	return b/=c;
}

bool operator <(const Point &a,const Point &b){
	return (a.x==b.x)?(a.y<b.y):(a.x<b.x);
}

bool operator >(const Point &a,const Point &b){
	return b<a;
}

double dot(const Point &a,const Point &b){
	return a.x*b.x+a.y*b.y;
}

double cross(const Point &a,const Point &b){
	return a.x*b.y-a.y*b.x;
}

double norm2(const Point &a){
	return dot(a,a);
}

int ccw(const Point &a,Point b,Point c){
	b-=a,c-=a;
	double rotdir=cross(b,c);
	if(rotdir>EPS)		return CCW;
	if(rotdir<-EPS)		return CW;
	return ON;
}

inline void calc_abc(const Line &l,double &a,double &b,double &c){	// l : ax+by+c=0
	a=l[0].y-l[1].y;
	b=l[1].x-l[0].x;
	c=l[0].x*l[1].y-l[1].x*l[0].y;
}

Point perp_foot(const Point &p,const Line &l){
	double a,b,c;
	calc_abc(l,a,b,c);
	return p-(a*p.x+b*p.y+c)/(a*a+b*b)*Point(a,b);
}

bool intersect(const Line &l,const Line &m,Point *p=NULL){
	// this routine also returns true in case "M is on L", etc,.
	if(abs(cross(l[1]-l[0],m[1]-m[0]))>EPS
	|| abs(cross(l[1]-l[0],m[0]-l[0]))<EPS){
		if(p){
			double a1,b1,c1,a2,b2,c2;
			calc_abc(l,a1,b1,c1);
			calc_abc(m,a2,b2,c2);
			double det=a1*b2-a2*b1;
			if(abs(det)<EPS)	*p=l[0];	// l == m
			else{
				p->x=(b1*c2-b2*c1)/det;
				p->y=(a2*c1-a1*c2)/det;
			}
		}
		return true;
	}
	return false;
}

bool intersect(const Segment &s,const Segment &t,Point *p=NULL){
	if(max(s[0].x,s[1].x)<min(t[0].x,t[1].x)
	|| max(t[0].x,t[1].x)<min(s[0].x,s[1].x)
	|| max(s[0].y,s[1].y)<min(t[0].y,t[1].y)
	|| max(t[0].y,t[1].y)<min(s[0].y,s[1].y))	return false;

	if(ccw(s[0],s[1],t[0])*ccw(s[0],s[1],t[1])<=0
	&& ccw(t[0],t[1],s[0])*ccw(t[0],t[1],s[1])<=0){
		if(p){
			double a1,b1,c1,a2,b2,c2;
			calc_abc(s,a1,b1,c1);
			calc_abc(t,a2,b2,c2);
			double det=a1*b2-a2*b1;
			if(abs(det)<EPS){	// s is parallel to t
				Point q[3]={s[0],s[1],t[0]};
				for(int i=0;i<3;i++){
					if(dot(q[i]-s[0],q[i]-s[1])<EPS && dot(q[i]-t[0],q[i]-t[1])<EPS){
						*p=q[i];
						break;
					}
				}
			}
			else{
				p->x=(b1*c2-b2*c1)/det;
				p->y=(a2*c1-a1*c2)/det;
			}
		}
		return true;
	}
	return false;
}

double area(const Point &a,const Point &b,const Point &c){
	return abs(cross(b-a,c-a))/2;
}

/**************** Library END ****************/

#include<cstdio>

using namespace std;

int main(){
	for(int n;scanf("%d",&n),n;){
		double a[30],b[30],c[30],d[30];
		for(int i=0;i<n;i++)	scanf("%lf",a+i);
		for(int i=0;i<n;i++)	scanf("%lf",b+i);
		for(int i=0;i<n;i++)	scanf("%lf",c+i);
		for(int i=0;i<n;i++)	scanf("%lf",d+i);

		Point p[32][32];
		p[0][0]=Point(0,0);
		p[0][n+1]=Point(1,0);
		p[n+1][0]=Point(0,1);
		p[n+1][n+1]=Point(1,1);
		for(int i=0;i<n;i++)	p[0][i+1]=Point(a[i],0);
		for(int i=0;i<n;i++)	p[n+1][i+1]=Point(b[i],1);
		for(int i=0;i<n;i++)	p[i+1][0]=Point(0,c[i]);
		for(int i=0;i<n;i++)	p[i+1][n+1]=Point(1,d[i]);
		for(int i=0;i<n;i++)for(int j=0;j<n;j++){
			intersect(Segment(p[0][j+1],p[n+1][j+1]),Segment(p[i+1][0],p[i+1][n+1]),&p[i+1][j+1]);
		}

		double amax=0;
		for(int i=0;i<n+1;i++)for(int j=0;j<n+1;j++){
			double ar=area(p[i][j],p[i][j+1],p[i+1][j+1])+area(p[i+1][j+1],p[i+1][j],p[i][j]);
			amax=max(amax,ar);
		}
		printf("%.9f\n",amax);
	}

	return 0;
}

Measured memory_bytes: 0