POJ 2722 Angle and Squares G++

#include <iostream>
#include <iomanip>
using namespace std;
//抄博友好程序 
int main()
{
	while(1)
	{
		int n;
		cin>>n;
		if(n==0)
		{
			break;
		}
		double ax,ay,bx,by;
		cin>>ax>>ay>>bx>>by;
		double ak,bk;
		ak=ay/ax;
		bk=by/bx;
		if(ak<bk)
		{
			swap(ak,bk);
		}
		double L=0;
		double area=0;
		for(int i=0;i<n;i++)
		{
			double t;
			cin>>t;
			L=L+t;
			area=area+t*t;
		}
		double x1=(L*bk+L)/(ak-bk);
		double x2=(L*ak+L)/(ak-bk);
		double y1=x1*ak;
		double y2=x2*bk;
		cout<<fixed<<setprecision(3)<<x2*y1/2.0-x1*y2/2.0-area/2.0<<endl;
	}
	return 0;
}