1 #include <cstdio>
2 #include <cstdlib>
3 #include <cstring>
4 #include <iostream>
5 #include <algorithm>
6 #include <cmath>
7 #include <vector>
8 #include <deque>
9
10 using namespace std;
11
12 #define print(x) cout<<x<<endl
13 #define input(x) cin>>x
14
15 const double inf=1e100;
16 const double eps=1e-10;
17
18 inline int zero(double x)
19 {
20 if(x<-eps) return -1;
21 else if(fabs(x)<eps) return 0;
22 else return 1;
23 }
24
25 struct point
26 {
27 double x,y;
28 point(){}
29 point(double i_x,double i_y)
30 {
31 x=i_x;y=i_y;
32 }
33 friend bool operator == (const point& pa,const point& pb)
34 {
35 return (!zero(pa.x-pb.x)) && (!zero(pa.y-pb.y));
36 }
37 };
38
39 struct segment
40 {
41 point p1,p2;
42 segment(){}
43 segment(const point& i_p1,const point& i_p2)
44 {
45 p1=i_p1;p2=i_p2;
46 }
47 };
48
49 struct line
50 {
51 double a,b,c;
52 line(){}
53 line(double i_a,double i_b,double i_c)
54 {
55 a=i_a;b=i_b;c=i_c;
56 }
57 };
58
59 inline double xmult(point sp,point ep,point op)
60 {
61 return ((sp.x-op.x)*(ep.y-op.y)-(sp.y-op.y)*(ep.x-op.x));
62 }
63
64 line makeline(point p1,point p2)
65 {
66 line res;
67 int sig=1;
68 res.a=p2.y-p1.y;
69 if(zero(res.a)<0)
70 {
71 sig=-1;
72 res.a=sig*res.a;
73 }
74 res.b=sig*(p1.x-p2.x);
75 res.c=sig*(p1.y*p2.x-p2.y*p1.x);
76 return res;
77 }
78
79 line makeline(segment s)
80 {
81 return makeline(s.p1,s.p2);
82 }
83
84 bool lineIntersect(line l1,line l2,point &p)
85 {
86 double d=l1.a*l2.b-l2.a*l1.b;
87 if(fabs(d)<eps) return false;
88 else
89 {
90 p.x = (l2.c*l1.b-l1.c*l2.b)/d;
91 p.y = (l2.a*l1.c-l1.a*l2.c)/d;
92 return true;
93 }
94 }
95
96 bool segIntersect(segment s1,segment s2,point &p)
97 {
98 if( (max(s1.p1.x,s1.p2.x)>=min(s2.p1.x,s2.p2.x)) &&
99 (max(s1.p1.y,s1.p2.y)>=min(s2.p1.y,s2.p2.y)) &&
100 (max(s2.p1.x,s2.p2.x)>=min(s1.p1.x,s1.p2.x)) &&
101 (max(s2.p1.y,s2.p2.y)>=min(s1.p1.y,s1.p2.y)) &&
102 !zero(xmult(s1.p1,s2.p1,s2.p2) * xmult(s1.p2,s2.p1,s2.p2)) &&
103 !zero(xmult(s2.p1,s1.p1,s1.p2) * xmult(s2.p2,s1.p1,s1.p2)))
104 {
105 lineIntersect(makeline(s1),makeline(s2),p);
106 return true;
107 }
108 else return false;
109 }
110
111 struct polygen
112 {
113 deque<point> pvec;
114
115 //如果是顺时针序，则clockwise=true
116 //否则是将其设为false
117 void push_point(const point& i_p,bool clockwise=true)
118 {
119 if(clockwise) pvec.push_back(i_p);
120 else pvec.push_front(i_p);
121 }
122
123 void KernelCut(segment s)
124 {
125 deque<point> core;
126 int sz=(int)pvec.size();
127 for(int i=0;i<sz;i++)
128 {
129 if(zero(xmult(pvec[i],s.p2,s.p1))>=0)
130 {
131 core.push_back(pvec[i]);
132 }
133 else
134 {
135 point cp;
136 if(zero(xmult(pvec[i],s.p2,s.p1) * xmult(pvec[(i-1+sz)%sz],s.p2,s.p1))<0)
137 {
138 line l1=makeline(s);
139 line l2=makeline(pvec[i],pvec[(i-1+sz)%sz]);
140 lineIntersect(l1,l2,cp);
141 core.push_back(cp);
142 }
143
144 if(zero(xmult(pvec[i],s.p2,s.p1) * xmult(pvec[(i+1)%sz],s.p2,s.p1))<0)
145 {
146 line l1=makeline(s);
147 line l2=makeline(pvec[i],pvec[(i+1)%sz]);
148 lineIntersect(l1,l2,cp);
149 core.push_back(cp);
150 }
151 }
152 }
153 pvec=core;
154 }
155
156 void getKernel()
157 {
158 deque<point> backup;
159 backup=pvec;
160 int sz=backup.size();
161 for(int i=0;i<sz;i++)
162 {
163 KernelCut(segment(backup[i],backup[(i+1)%sz]));
164 }
165 }
166 };
167
168 int main()
169 {
170 int n;
171 double a,b;
172 while(input(n) && n)
173 {
174 polygen poly;
175 for(int i=0;i<n;i++)
176 {
177 input(a>>b);
178 poly.push_point(point(a,b),false);
179 }
180 poly.getKernel();
181 if(poly.pvec.size()>0) print(1);
182 else print(0);
183 }
184 return 0;
185 }
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