> #include <cstdio>
> #include <algorithm>
> using namespace std;
> typedef struct
> {
> 	double x;
> 	double y;
> }Point;
> 
> typedef struct
> {
> 	Point pt1;
> 	Point pt2;
> }Segment;
> 
> Point pt;
> double left[100],right[100],top[100],bottom[100];
> Point mid[1000];
> Segment sgmt[31];
> 
> double multi(Point p1, Point p2, Point p0)
> {
>     //求矢量[p0, p1], [p0, p2]的叉积
>     //p0是顶点 
>     return (p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y);
>     //若结果等于0，则这三点共线
>     //若结果大于0，则p0p2在p0p1的逆时针方向
>     //若结果小于0，则p0p2在p0p1的顺时针方向 
> }
> 
> double max(double x, double y)
> {
>     //比较两个数的大小，返回大的数
>     return  x > y ? x : y;
> }
> 
> double min(double x, double y)
> {
>     //比较两个数的大小，返回小的数
> 	return  x < y ? x : y;
> }
> 
> bool isIntersected(Point s1, Point e1, Point s2, Point e2)
> {
>     //判断线段是否相交
>     //1.快速排斥试验判断以两条线段为对角线的两个矩形是否相交 
>     //2.跨立试验
>     if(
>     (max(s1.x, e1.x) >= min(s2.x, e2.x)) &&
>     (max(s2.x, e2.x) >= min(s1.x, e1.x)) &&
>     (max(s1.y, e1.y) >= min(s2.y, e2.y)) &&
>     (max(s2.y, e2.y) >= min(s1.y, e1.y)) &&
>     (multi(s2, e1, s1) * multi(e1, e2, s1) >= 0) &&
>     (multi(s1, e2, s2) * multi(e2, e1, s2) >= 0)
>     )  
> 		return true;
>     
>     return false;    
> }
> 
> int main()
> {
> 	int n,i,j;
> 	int lf = 1,rt = 1,tp = 1,btm = 1;
> 	int counter = 0;
> 	int res,min = 99999999;
> 
> 	left[0] = 0;
> 	right[0] = 0;
> 	top[0] = 0;
> 	bottom[0] = 0;
> 
> 	scanf("%d",&n);
> 	for(i = 0; i < n; i ++)
> 	{
> 		scanf("%lf%lf",&pt.x,&pt.y);
> 		sgmt[i].pt1.x = pt.x;
> 		sgmt[i].pt1.y = pt.y;
> 		if(pt.x == 0)
> 			left[lf++] = pt.y;
> 		if(pt.x == 100)
> 			right[rt++] = pt.y;
> 		if(pt.y == 0)
> 			bottom[btm++] = pt.x;
> 		if(pt.y == 100)
> 			top[tp++] = pt.x;
> 		scanf("%lf%lf",&pt.x,&pt.y);
> 		sgmt[i].pt2.x = pt.x;
> 		sgmt[i].pt2.y = pt.y;
> 		if(pt.x == 0)
> 			left[lf++] = pt.y;
> 		if(pt.x == 100)
> 			right[rt++] = pt.y;
> 		if(pt.y == 0)
> 			bottom[btm++] = pt.x;
> 		if(pt.y == 100)
> 			top[tp++] = pt.x;
> 	}
> 	scanf("%lf%lf",&pt.x,&pt.y);//宝物的坐标
> 
> 	left[lf++] = 100;
> 	right[rt++] = 100;
> 	top[tp++] = 100;
> 	bottom[btm++] = 100;
> 
> 	sort(left,left+lf);
> 	sort(right,right+rt);
> 	sort(top,top+tp);
> 	sort(bottom,bottom+btm);
> 
> 	for(i = 0; i < lf-1; i++)//求中点
> 	{
> 		mid[counter].x = 0;
> 		mid[counter].y = ( left[i] + left[i+1] ) / 2;
> 		counter++;
> 	}
> 	for(i = 0; i < rt-1; i++)
> 	{
> 		mid[counter].x = 100;
> 		mid[counter].y = ( right[i] + right[i+1] ) / 2;
> 		counter++;
> 	}
> 	for(i = 0; i < tp-1; i++)
> 	{
> 		mid[counter].y = 100;
> 		mid[counter].x = ( top[i] + top[i+1] ) / 2;
> 		counter++;
> 	}
> 	for(i = 0; i < btm-1; i++)
> 	{
> 		mid[counter].y = 0;
> 		mid[counter].y = ( bottom[i] + bottom[i+1] ) / 2;
> 		counter++;
> 	}
> 
> 	for(i = 0; i < counter; i++)
> 	{
> 		printf("%lf    %lf\n",mid[i].x,mid[i].y);
> 		res = 0;
> 		for(j = 0; j < n; j++)
> 		{
> 			if(isIntersected(sgmt[j].pt1,sgmt[j].pt2,pt,mid[i]))
> 				res++;
> 		}
> 		if(res < min)
> 			min = res;
> 	}
> 
> 	printf("Number of doors = %d\n",min+1);
> 	return 0;
> }