Poj Solution 2812

http://poj.org/problem?id=2812

//* @author: ccQ.SuperSupper
import java.io.*;
import java.util.*;
class POINT{
    double x,y;
}
public class Main {
    static final int N = 100000;
    static POINT point[] = new POINT[N];
    static int n;
    static void start(){
        for(int i=0;i< N;++i) point[i] = new POINT();
    }
    static double Get_Num(StreamTokenizer cin) throws Exception{
        cin.nextToken();
        return cin.nval;
    }
    
public static void main(String[]args) throws Exception{
  int i;
  double V;
  start();
  StreamTokenizer cin = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
  while(true){
        n = (int) Get_Num(cin);
        if(n< 3) break;
        for(i=0;i< n;++i){
            point[i].x = Get_Num(cin);
            point[i].y = Get_Num(cin);
        }
        V = Get_Num(cin);
        System.out.printf("BAR LENGTH: %.2fn",solve(V));
    }
    }
    
 static double corss(POINT a,POINT b,POINT c){
        return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
    }
    static double solve(double V){
        double ans=0.0;
        for(int i=2;i< n;++i){
            ans+=corss(point[0],point[i-1],point[i]);
        }
        ans = ans< 0.0?ans/-2.0:ans/2.0;
        return V/ans;
    }
}