http://poj.org/problem?id=1408
/* @author:����acmilan_fan@yahoo.cn */
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Main {
static double[][][] mesh=new double[32][32][2];
public static void main(String[] args) throws Exception{
BufferedReader br = new BufferedReader(new
InputStreamReader(System.in));
String s;
String[] ss;
int n,i,j;
double max=0d,t;
while((s=br.readLine())!=null&&!"0".equals(s)){
n=parseInt(s);
s=br.readLine();
ss=s.split(" ",n);
for(i=1;i<=n;i++){
mesh[n+1][i][0] = Double.parseDouble(ss[i-1]);
}
s=br.readLine();
ss=s.split(" ",n);
for(i=1;i<=n;i++){
mesh[0][i][0] = Double.parseDouble(ss[i-1]);
mesh[0][i][1] = 1d;
}
s=br.readLine();
ss=s.split(" ",n);
for(i=0;i< n;i++){
mesh[n-i][0][1] = Double.parseDouble(ss[i]);
}
s=br.readLine();
ss=s.split(" ",n);
for(i=0;i< n;i++){
mesh[n-i][n+1][0] = 1d;
mesh[n-i][n+1][1] = Double.parseDouble(ss[i]);
}
mesh[0][0][1]=
mesh[0][n+1][0]=mesh[0][n+1][1]=
mesh[n+1][n+1][0]=1d;
for(i=1;i<=n;i++){
for(j=1;j<=n;j++){
setPoint(mesh[n+1][j][0],mesh[0][j][0],mesh[i][0][1],mesh[i][n+1][1],i,j);
}
}
for(i=0;i<=n;i++){
for(j=0;j<=n;j++){
t=getSquare(mesh[i][j],mesh[i][j+1],mesh[i+1][j+1],mesh[i+1][j]);
if(t>max)
max=t;
}
}
System.out.printf("%.6fn",max);
max=0d;
reset(n+2);
}
}
static void print(int n) {
for(int i=0;i< n;i++){
for(int j=0;j< n;j++){
System.out.print("["+mesh[i][j][0]+","+mesh[i][j][1]+"]");
}
System.out.println();
}
}
static void setPoint(double a,double b,double c,double d,int x,int y){
double t=1-(a-b)*(c-d);
mesh[x][y][0]=(a-(a-b)*c)/t;
mesh[x][y][1]=(c-a*(c-d))/t;
}
static double getSquare(double[] a,double[] b,double[] c,double[] d){
double t=Math.abs((a[0]-b[0])*(c[1]-b[1])-(a[1]-b[1])*(c[0]-b[0]));
t+=Math.abs((a[0]-d[0])*(c[1]-d[1])-(a[1]-d[1])*(c[0]-d[0]));
return t/2;
}
static void reset(int limit){
for(int i=0;i< limit;i++){
for(int j=0;j< limit;j++){
mesh[i][j][0]=mesh[i][j][1]=0d;
}
}
}
static int parseInt(String s){
int t = 0;
for(char ch: s.toCharArray()){
t *= 10;
t += ch-'0';
}
return t;
}
}