dcmp(v[i%n].x-x)<=0&&dcmp(v[(i+1)%n].x-x)>0

dcmp(v[i%n].x-x)>0&&dcmp(v[(i+1)%n].x-x)<=0

#include<iostream>

#include<cstdio>

#include<cstdlib>

#include<cstring>

#include<ctime>

#include<cmath>

#include<algorithm>

#include<queue>

#include<set>

#include<map>

#include<iomanip>

using namespace std;

#define LL long long

#define up(i,j,n) for(int i=j;i<=n;i++)

#define pii pair<int,int>

#define db double

#define eps 1e-4

#define FILE "dealing"

int read(){

	int x=0,f=1,ch=getchar();

	while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}

	while(ch<='9'&&ch>='0'){x=(x<<1)+(x<<3)+ch-'0',ch=getchar();}

	return x*f;

}

const int maxn=22000,inf=1000000000;

bool cmin(db& a,db b){return a>b?a=b,true:false;}

int n;

struct vec {

	db x,y;

	vec(db x=0,db y=0):x(x),y(y){}

}v[maxn];

int dcmp(db v){if(fabs(v)<eps)return 0;return v<0?-1:1;}

db x,y;

db s[5];

db gety(vec v,vec b,db x){

	db k=(b.y-v.y)/(b.x-v.x);

	db d=v.y-v.x*k;

	return x*k+d;

}

int main(){

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

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

	n=read();

	up(i,0,n-1)v[i].x=read(),v[i].y=read();

	x=read(),y=read();

	int wn=1;db ans=0,last=y;

	db Min=inf;int k=0;

	up(i,0,n-1)

	if(((v[i%n].x<x&&v[(i+1)%n].x>x)||(v[i%n].x>x&&v[(i+1)%n].x<x))&&gety(v[i%n],v[(i+1)%n],x)>y&&cmin(Min,gety(v[i],v[(i+1)%n],x)-y)){k=i;}

	up(i,k,k+n-1){

		if(dcmp(v[i%n].x-x)<=0&&dcmp(v[(i+1)%n].x-x)>0&&dcmp(gety(v[i%n],v[(i+1)%n],x)-y)>0){

			s[wn]+=gety(v[i%n],v[(i+1)%n],x)-last;

			last=gety(v[i%n],v[(i+1)%n],x);

			wn++;

		}

		else if(dcmp(v[i%n].x-x)>0&&dcmp(v[(i+1)%n].x-x)<=0&&dcmp(gety(v[i%n],v[(i+1)%n],x)-y)>0){

			s[wn]+=gety(v[i%n],v[(i+1)%n],x)-last;

			last=gety(v[i%n],v[(i+1)%n],x);

			wn--;

		}

	}

	if(wn==1)printf("%d\n",(int)fabs(s[2]+s[0]));

	else printf("%d\n",fabs(s[1]));

	return 0;

}