/************************************************

* Author        :Running_Time

* Created Time  :2015/11/4 星期三 11:13:29

* File Name     :POJ_3348.cpp

 ************************************************/

#include <cstdio>

#include <algorithm>

#include <iostream>

#include <sstream>

#include <cstring>

#include <cmath>

#include <string>

#include <vector>

#include <queue>

#include <deque>

#include <stack>

#include <list>

#include <map>

#include <set>

#include <bitset>

#include <cstdlib>

#include <ctime>

using namespace std;

#define lson l, mid, rt << 1

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

typedef long long ll;

const int N = 1e5 + 10;

const int INF = 0x3f3f3f3f;

const int MOD = 1e9 + 7;

const double EPS = 1e-10;

const double PI = acos (-1.0);

int dcmp(double x)  {

    if (fabs (x) < EPS) return 0;

    else    return x < 0 ? -1 : 1;

}

struct Point    {

    double x, y;

    Point () {}

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

    Point operator - (const Point &r) const {

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

    }

    bool operator < (const Point &r) const  {

        return x < r.x || (x == r.x && y < r.y);

    }

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

        return dcmp (x - r.x) == 0 && dcmp (y - r.y) == 0;

    }

};

typedef Point Vector;

Point read_point(void)  {

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

    return Point (x, y);

}

double dot(Point a, Point b)    {

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

}

double cross(Vector A, Vector B)    {

    return A.x * B.y - A.y * B.x;

}

bool on_seg(Point p, Point a, Point b)    {

    return dcmp (cross (a - p, b - p)) == 0 && dcmp (dot (a - p, b - p)) < 0;

}

double area_poly(vector<Point> ps)  {

    double ret = 0;

    for (int i=1; i<ps.size ()-1; ++i)  {

        ret += fabs (cross (ps[i] - ps[0], ps[i+1] - ps[0])) / 2;

    }

    return ret;

}

/*

    凸包边上无点：<=    凸包边上有点：<

*/

vector<Point> convex_hull(vector<Point> ps)   {

    sort (ps.begin (), ps.end ());

    int n = ps.size (), k = 0;

    vector<Point> qs (n * 2);

    for (int i=0; i<n; ++i) {

        while (k > 1 && cross (qs[k-1] - qs[k-2], ps[i] - qs[k-1]) <= 0)    k--;

        qs[k++] = ps[i];

    }

    for (int t=k, i=n-2; i>=0; --i) {

        while (k > t && cross (qs[k-1] - qs[k-2], ps[i] - qs[k-1]) <= 0)     k--;

        qs[k++] = ps[i];

    }

    qs.resize (k - 1);

    return qs;

}

int main(void)    {

    int n;

    while (scanf ("%d", &n) == 1)   {

        vector<Point> ps;

        for (int i=0; i<n; ++i) ps.push_back (read_point ());

        vector<Point> qs = convex_hull (ps);

        double area = area_poly (qs);

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

    }

   //cout << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";

    return 0;

}