#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
using namespace std;

struct Point {
    int x, y;
    Point(int x = 0, int y = 0) : x(x), y(y) {}
    bool operator<(const Point &p) const {
        return x < p.x || (x == p.x && y < p.y);
    }
};

// 计算叉积
int cross(const Point &O, const Point &A, const Point &B) {
    return (A.x - O.x) * (B.y - O.y) - (A.y - O.y) * (B.x - O.x);
}

// 计算凸包
vector<Point> convexHull(vector<Point> &points) {
    int n = points.size(), k = 0;
    vector<Point> hull(2 * n);
    sort(points.begin(), points.end());
    for (int i = 0; i < n; ++i) {
        while (k >= 2 && cross(hull[k-2], hull[k-1], points[i]) <= 0) k--;
        hull[k++] = points[i];
    }
    for (int i = n-2, t = k+1; i >= 0; --i) {
        while (k >= t && cross(hull[k-2], hull[k-1], points[i]) <= 0) k--;
        hull[k++] = points[i];
    }
    hull.resize(k-1);
    return hull;
}

// 计算多边形面积
double calculateArea(const vector<Point> &polygon) {
    double area = 0.0;
    int n = polygon.size();
    for (int i = 0; i < n; ++i) {
        int j = (i + 1) % n;
        area += polygon[i].x * polygon[j].y - polygon[j].x * polygon[i].y;
    }
    return fabs(area) / 2.0;
}

int main() {
    int N, M;
    cin >> N >> M;
    vector<Point> points(N);
    for (int i = 0; i < N; ++i) {
        cin >> points[i].x >> points[i].y;
    }
    vector<Point> hull = convexHull(points);
    int hullSize = hull.size();
    M = min(M, hullSize);
    double maxArea = 0.0;
    // 遍历所有可能的子集
    for (int mask = 1; mask < (1 << hullSize); ++mask) {
        if (__builtin_popcount(mask) > M) continue;
        vector<Point> selected;
        for (int i = 0; i < hullSize; ++i) {
            if (mask & (1 << i)) {
                selected.push_back(hull[i]);
            }
        }
        vector<Point> subHull = convexHull(selected);
        double area = calculateArea(subHull);
        if (area > maxArea) {
            maxArea = area;
        }
    }
    cout << fixed << setprecision(1) << maxArea << endl;
    return 0;
}