#include <bits/stdc++.h>
using namespace std;
const int MAXN = 205;
const int MAXM = 55;
struct Point {
  int x, y;
  double k;
  Point(int _x = 0, int _y = 0) { x = _x, y = _y; }
  Point operator-(const Point &b) const { return Point(x - b.x, y - b.y); }
  bool operator<(const Point &b) const { return k < b.k; }
  long long operator*(const Point &b) const {
    return 1LL * x * b.y - 1LL * y * b.x;
  }
} a[MAXN], p[MAXN];
int n, m;
long long ans, mx[MAXM], f[MAXN][MAXN][MAXM];
vector<int> adj[MAXN], rev[MAXN];
queue<int> q[MAXN];
bool Onleft(Point a, Point b, Point c) { return (b - a) * (c - b) > 0; }
void Add(int x, int y) {
  while (!q[x].empty() && Onleft(p[q[x].front()], p[x], p[y]))
    Add(q[x].front(), y), q[x].pop();
  rev[x].push_back(y);
  adj[y].push_back(x);
  q[y].push(x);
}
void Init(int n) {
  for (int i = 1; i <= n; i++) {
    adj[i].clear(), rev[i].clear();
    while (!q[i].empty()) q[i].pop();
  }
  for (int i = 1; i < n; i++) Add(i, i + 1);
}
void Dp(int n) {
  memset(f, 0, sizeof(f));
  for (int i = n; i; i--) {
    for (int j = 0; j < m; j++) mx[j] = 0;
    reverse(adj[i].begin(), adj[i].end());
    int cur = rev[i].size() - 1;
    for (auto j : adj[i]) {
      f[j][i][1] = p[j] * p[i];
      for (int k = 2; k <= m; k++)
        if (mx[k - 1]) f[j][i][k] = mx[k - 1] + p[j] * p[i];
      for (; ~cur && Onleft(p[j], p[i], p[rev[i][cur]]); cur--)
        for (int k = 1; k < m; k++)
          if (mx[k] < f[i][rev[i][cur]][k])
            mx[k] = f[i][rev[i][cur]][k], f[j][i][k + 1] = mx[k] + p[j] * p[i];
    }
  }
  for (int i = 1; i <= n; i++)
    for (auto j : rev[i]) ans = max(ans, f[i][j][m - 2]);
}
void Solve(int idx) {
  int cnt = 0;
  for (int i = 1; i <= n; i++)
    if (i ^ idx)
      if (a[i].x > a[idx].x || (a[i].x == a[idx].x && a[i].y > a[idx].y))
        p[++cnt] = a[i] - a[idx], p[cnt].k = atan2(p[cnt].y, p[cnt].x);
  sort(p + 1, p + cnt + 1);
  Init(cnt);
  Dp(cnt);
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) scanf("%d%d", &a[i].x, &a[i].y);
  for (int i = 1; i <= n; i++) Solve(i);
  cout << ans / 2 << "." << (ans & 1 ? "50" : "00") << endl;
  return 0;
}
