use proconio::input;

const DIFFS: [(f64, f64); 4] = [(1.0, 0.0), (-1.0, 0.0), (0.0, 1.0), (0.0, -1.0)];

fn main() {
    input! {
        triangle: [(f64, f64); 3],
    }

    let mut ans = 0.0;
    let mut stack: Vec<Vec<(f64, f64)>> = vec![vec![]];
    while let Some(apexes) = stack.pop() {
        if apexes.len() == 3 {
            let area = calc_area(&apexes);
            if area > ans {
                ans = area;
            }

            continue;
        }

        let apex_idx = apexes.len();
        for (dx, dy) in DIFFS {
            let mut apexes = apexes.clone();
            let (x, y) = triangle[apex_idx];
            apexes.push((x + dx, y + dy));

            stack.push(apexes);
        }
    }

    println!("{}", ans);
}

fn calc_area(triangle: &[(f64, f64)]) -> f64 {
    let (x0, y0) = triangle[0];
    let (x1, y1) = triangle[1];
    let (x2, y2) = triangle[2];

    let (dx1, dy1) = (x1 - x0, y1 - y0);
    let (dx2, dy2) = (x2 - x0, y2 - y0);

    (dx1 * dy2 - dx2 * dy1).abs() / 2.0
}