use proconio::input;

fn area (points: &Vec<f64>) -> f64{
    let a = points[2]-points[0];
    let b = points[3]-points[1];
    let c = points[4]-points[0];
    let d = points[5]-points[1];
    (a*d - b*c).abs() / 2.0
}

fn main () {
    input! {
        mut points: [f64;6],
    }
    let mut ans = -1.0;
    for bit_mp in 0..(1<<3) {
        for bit_xy in 0..(1<<3) {
            for p in 0..3 {
                match (bit_mp & (1<<p), bit_xy & (1<<p)) {
                    (0,0) => points[2*p] -= 1.0,
                    (_,0) => points[2*p] += 1.0,
                    (0,_) => points[2*p+1] -= 1.0,
                    (_,_) => points[2*p+1] += 1.0,
                    
                }
            }
            //println!("bit_mp: {}, bit_xy: {}", bit_mp, bit_xy);
            //println!("{:?}", points);
            ans = f64::max(ans, area(&points));
            //println!("{}", ans);
            for p in 0..3 {
                match (bit_mp & (1<<p), bit_xy & (1<<p)) {
                    (0,0) => points[2*p] += 1.0,
                    (_,0) => points[2*p] -= 1.0,
                    (0,_) => points[2*p+1] += 1.0,
                    (_,_) => points[2*p+1] -= 1.0,
                    
                }
            }
        }
    }
    println!("{:.10}", ans as f64);
}