#include <bits/stdc++.h>
using namespace std;
const int64_t LINF = 1LL << 62;
struct Point {
  int x, y;
  bool operator<(const Point& o) const {
    return x < o.x || (x == o.x && y < o.y);
  }
};
inline int64_t cross(const Point& o, const Point& a, const Point& b) {
  return (a.x - o.x) * (int64_t)(b.y - o.y) -
         (a.y - o.y) * (int64_t)(b.x - o.x);
}
int64_t solve(vector<Point> a, int m) {
  int n = ((int)(a).size());
  Point o = a[0];
  sort(a.begin() + 1, a.end(),
       [o](const Point& a, const Point& b) { return cross(o, a, b) > 0; });
  vector<vector<int>> works(n);
  vector<vector<vector<int64_t>>> dp(n);
  works[0] = {0};
  dp[0] = vector<vector<int64_t>>(1, vector<int64_t>(m + 1, -LINF));
  dp[0][0][1] = 0;
  int64_t ans = 0;
  for (int i = 1; i < n; ++i) {
    for (int j = i - 1; j > 0; --j) {
      if (works[i].empty() || cross(a[i], a[works[i].back()], a[j]) < 0) {
        works[i].push_back(j);
      }
    }
    works[i].push_back(0);
    reverse(works[i].begin(), works[i].end());
    dp[i] = vector<vector<int64_t>>(((int)(works[i]).size()),
                                    vector<int64_t>(m + 1, -LINF));
    for (int j = 0; j < ((int)(works[i]).size()); ++j) {
      int prev = works[i][j];
      int pos = 0, step = 1;
      while (step < ((int)(works[prev]).size())) {
        step *= 2;
      }
      for (; step > 0; step /= 2) {
        if (pos + step < ((int)(works[prev]).size()) &&
            cross(a[i], a[prev], a[works[prev][pos + step]]) <= 0) {
          pos += step;
        }
      }
      for (int k = 2; k <= m; ++k) {
        dp[i][j][k] = max(j == 0 ? -LINF : dp[i][j - 1][k],
                          dp[prev][pos][k - 1] + cross(o, a[prev], a[i]));
      }
    }
    ans = max(ans, dp[i].back().back());
  }
  return ans;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  vector<Point> a(n);
  for (int i = 0; i < n; ++i) {
    cin >> a[i].x >> a[i].y;
  }
  sort(a.begin(), a.end());
  int64_t ans = 0;
  for (int i = 0; i < n; ++i) {
    ans = max(ans, solve(vector<Point>(a.begin() + i, a.end()), m));
  }
  cout << ans / 2;
  if (ans % 2 == 0) {
    cout << ".00\n";
  } else {
    cout << ".50\n";
  }
}
