#include<cstdio>

 #include<iostream>

 #include<cstring>

 #include<algorithm>

 #include<queue>

 #include<set>

 #include<map>

 #include<stack>

 #include<time.h>

 #include<cstdlib>

 #include<cmath>

 #include<list>

 using namespace std;

 #define MAXN 100100

 #define eps 1e-9

 #define For(i,a,b) for(int i=a;i<=b;i++)

 #define Fore(i,a,b) for(int i=a;i>=b;i--)

 #define lson l,mid,rt<<1

 #define rson mid+1,r,rt<<1|1

 #define mkp make_pair

 #define pb push_back

 #define cr clear()

 #define sz size()

 #define met(a,b) memset(a,b,sizeof(a))

 #define iossy ios::sync_with_stdio(false)

 #define fre freopen

 #define pi acos(-1.0)

 #define inf 1e6+7

 #define Vector Point

 const int Mod=1e9+;

 typedef unsigned long long ull;

 typedef long long ll;

 int dcmp(double x){

     if(fabs(x)<=eps) return ;

     return x<?-:;

 }

 struct Point{

     double x,y;

     int id;

     Point(double x=,double y=):x(x),y(y) {}

     bool operator < (const Point &a)const{

         if(x==a.x) return y<a.y;

         return x<a.x;

     }

     Point operator - (const Point &a)const{

         return Point(x-a.x,y-a.y);

     }

     Point operator + (const Point &a)const{

         return Point(x+a.x,y+a.y);

     }

     Point operator * (const double &a)const{

         return Point(x*a,y*a);

     }

     Point operator / (const double &a)const{

         return Point(x/a,y/a);

     }

     void read(){

         scanf("%lf%lf",&x,&y);

     }

     void out(){

         cout<<"debug: "<<x<<" "<<y<<endl;

     }

     bool operator == (const Point &a)const{

         return dcmp(x-a.x)== && dcmp(y-a.y)==;

     }

 };

 double Dot(Vector a,Vector b) {

     return a.x*b.x+a.y*b.y;

 }

 double dis(Vector a) {

     return sqrt(Dot(a,a));

 }

 double Cross(Point a,Point b){

     return a.x*b.y-a.y*b.x;

 }

 int n;

 Point p[];

 int ls,rs;

 int chk1(Point p1,Point p2,int pos){

     int l=pos+,r=pos+n-;

     while(l<r){

         int mid=l+r>>;

         if(dcmp(Cross(p[mid]-p[pos],p1-p[pos]))<= && dcmp(Cross(p[mid]-p[pos],p2-p[pos])<=)) r=mid;

         else l=mid+;

     }

     return l;

 }

 int chk2(Point p1,Point p2,int pos){

     int l=pos+,r=pos-+n;

     while(l<r){

         int mid=l+r+>>;

         if(dcmp(Cross(p[mid]-p[pos],p1-p[pos]))>= && dcmp(Cross(p[mid]-p[pos],p2-p[pos]))>=) l=mid;

         else r=mid-;

     }

     return l;

 }

 Point p1,p2;

 void solve(){

     For(i,,n) p[i].read();

     p1.read();p2.read();

     ll ans=;

     For(i,,n) p[i+n]=p[i];

     For(i,,n){

         ls=chk1(p1,p2,i);

         rs=chk2(p1,p2,i);

         if(ls!=rs)ans+=abs(ls-rs)-;

     }

     cout<<ans/<<endl;

 }

 int main(){

 //    fre("in.txt","r",stdin);

     freopen("kingdom.in","r",stdin);

     freopen("kingdom.out","w",stdout);

     int t=;

      while(~scanf("%d",&n) &&n)    solve();

     return ;

 }