#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  array<int, 3> x{}, y{};
  REP(i, 3) cin >> x[i] >> y[i];
  int ans = 0;
  const auto dfs = [&](auto dfs, const int i) -> void {
    if (i == 3) {
      chmax(ans, abs((x[1] - x[0]) * (y[2] - y[0]) - (x[2] - x[0]) * (y[1] - y[0])));
      return;
    }
    --x[i];
    dfs(dfs, i + 1);
    x[i] += 2;
    dfs(dfs, i + 1);
    --x[i];
    --y[i];
    dfs(dfs, i + 1);
    y[i] += 2;
    dfs(dfs, i + 1);
    --y[i];
  };
  dfs(dfs, 0);
  cout << ans / 2. << '\n';
  return 0;
}