#include<bits/stdc++.h>
using namespace std;
vector<int> dx = {1, 0, -1, 0};
vector<int> dy = {0, 1, 0, -1};
int main() {
  vector<int> x(3), y(3);
  for (int i = 0; i < 3; i++) {
    cin >> x[i] >> y[i];
  }
  double ans = 0;
  for (int i = 0; i < 4 * 4 * 4; i++) {
    int ni = i;
    int i0 = ni % 4;
    ni /= 4;
    int i1 = ni % 4;
    ni /= 4;
    int i2 = ni % 4;
    vector<int> nx = x;
    vector<int> ny = y;
    nx[0] = x[0] + dx[i0];
    nx[1] = x[1] + dx[i1];
    nx[2] = x[2] + dx[i2];
    ny[0] = y[0] + dy[i0];
    ny[1] = y[1] + dy[i1];
    ny[2] = y[2] + dy[i2];
    ans = max<double>(ans, abs((nx[0] - nx[2]) * (ny[1] - ny[2]) - (nx[1] - nx[2]) * (ny[0] - ny[2])));
    ans = max<double>(ans, abs((nx[1] - nx[0]) * (ny[2] - ny[0]) - (ny[1] - ny[0]) * (nx[2] - nx[0])));
  }
  ans /= 2;
  printf("%.1f\n",ans);
}