#include <vector>
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cassert>

using namespace std;

  vector<double> aa;
  vector<double> bb;
  vector<double> cc;
  vector<double> dd;
  
  int n;


typedef pair<double,double> t_pos;

t_pos cross(double a, double b, double c, double d)
{
  double ky = (a + (b-a)*c) / (1 - (b-a)*(d-c));
  double y = ky;
  double x = c + (d-c) * ky;
  assert(ky >= 0);
  assert(0 <= x && x <= 1.0);
  assert(0 <= y && y <= 1.0);
  return make_pair(x, y);
}

double surface_3(t_pos& p1, t_pos& p2, t_pos& p3){
  t_pos v1 = make_pair(p2.first-p1.first, p2.second-p1.second);
  t_pos v2 = make_pair(p3.first-p1.first, p3.second-p1.second);
  
  double len1 = sqrt(v1.first*v1.first + v1.second*v1.second);
  double len2 = sqrt(v2.first*v2.first + v2.second*v2.second);

  assert(len1 > 0.0);
  assert(len2 > 0.0);
  
  double dot = (v1.first * v2.first + v1.second * v2.second);
  double cosA = dot / (len1*len2);
  double sinA = sqrt(1.0 - cosA * cosA);
  double s = len1 * len2 * sinA / 2.0;

  assert(s > 0);
  
  //  cout << "base:" << base << ", naname:" << naname << " sur:" << s << endl;
  return s;
}


double surface_4(t_pos& p1, t_pos& p2, t_pos& p3, t_pos& p4){
  return surface_3(p1, p2, p4) + surface_3(p1, p3, p4);
}

double surface(int i, int j){
  double b1 = bb[i];
  double b2 = bb[i+1];
  double a1 = aa[i];
  double a2 = aa[i+1];
  double c1 = cc[j];
  double c2 = cc[j+1];
  double d1 = dd[j];
  double d2 = dd[j+1];

  double surface;

  t_pos p1, p2, p3, p4;
  p1 = cross(a1, b1, c1, d1);
  p2 = cross(a2, b2, c1, d1);
  p3 = cross(a1, b1, c2, d2);
  p4 = cross(a2, b2, c2, d2);
  //  printf("cross at (%f,%f)\n", p1.first, p1.second);

  double s = surface_4(p1, p2, p3, p4);
  //cout << s << endl;
  return s;
}
 

int main(){
  while (cin >> n){
    if (n == 0) break;
    aa.resize(n+2);
    bb.resize(n+2);
    cc.resize(n+2);
    dd.resize(n+2);
    aa[0] = 0.0;
    bb[0] = 0.0;
    cc[0] = 0.0;
    dd[0] = 0.0;
    for (int i=0; i<n; ++i) cin >> aa[i+1];
    for (int i=0; i<n; ++i) cin >> bb[i+1];
    for (int i=0; i<n; ++i) cin >> cc[i+1];
    for (int i=0; i<n; ++i) cin >> dd[i+1];
    aa[n+1] = 1.0;
    bb[n+1] = 1.0;
    cc[n+1] = 1.0;
    dd[n+1] = 1.0;

    double max_surface = 0.0;
    double total = 0.0;
    for (int i=0; i<=n; ++i){
      for (int j=0; j<=n; ++j){
	double s = surface(i, j);
	//	printf("surf at (%d, %d) is %f\n", i, j, s);
	total += s;
	max_surface = max(max_surface, s);
      }
    }

    printf("%.6f\n", max_surface);
  }

  
  return 0;
}