// poj3348

#include<algorithm>

#include<iostream>

#include<cstring>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<map>

#define inf 2147483640

#define LL long long

#define Pi acos(-1.0)

#define free(a) freopen(a".in","r",stdin);freopen(a".out","w",stdout);

using namespace std;

inline LL getint() {

    LL x=0,f=1;char ch=getchar();

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

    while (ch>='0' && ch<='9') {x=x*10+ch-'0';ch=getchar();}

    return x*f;

}

const int maxn=10010;

struct point {int x,y;}p[maxn];

int s[maxn],n,top;

int cross(point p0,point a,point b) {

    return (a.x-p0.x)*(b.y-p0.y)-(a.y-p0.y)*(b.x-p0.x);

}

double dis(point a,point b) {

    return sqrt((double)(a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));

}

bool cmp(point a,point b) {

    int t=cross(p[1],a,b);

    if (t>0) return 1;

    else if (t==1 && dis(a,p[1])<dis(b,p[1])) return 1;

    else return 0;

}

void Graham() {

    if (n==1) s[top=1]=1;

    else if (n==2) {s[top=1]=1;s[++top]=2;}

    else {

        s[top=1]=1;s[++top]=2;

        for (int i=3;i<=n;i++) {

            while (top>1 && cross(p[s[top-1]],p[s[top]],p[i])<=0) top--;

            s[++top]=i;

        }

    }

}

double Size() {

    point p0=p[s[1]];

    double sum=0;

    for (int i=3;i<=top;i++) sum+=cross(p0,p[s[i-1]],p[s[i]]);

    return sum/2;

}

int main() {

    while (scanf("%d",&n)!=EOF) {

        int k=1;

        for (int i=1;i<=n;i++) {

            scanf("%d%d",&p[i].x,&p[i].y);

            if (p[i].x<p[k].x || (p[i].x==p[k].x && p[i].y<p[k].y)) k=i;

        }

        point p0=p[k];

        p[k]=p[1];p[1]=p0;

        sort(p+2,p+1+n,cmp);

        Graham();

        printf("%d\n",(int)Size()/50);

    }

    return 0;

}