#include <bits/stdc++.h>
using namespace std;

#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()

typedef long double LD;

struct point {
    LD x, y;
    point() {}
    point(LD _x, LD _y) : x(_x), y(_y) {}
};

vector < point > v(4);

void rotate()
{
    for(int i = 0; i < 5; i++)
    {
        v[i] = point(v[i].y, -v[i].x);
    }
}

LD ilo(point a, point b, point c)
{
    return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
}

LD pole(vector < point > &vec)
{
    LD ans = 0;
    for(int i = 0; i + 1 < sz(vec); i++)
    {
        ans += ilo(point(0, 0), vec[i], vec[i + 1]);
    }
    ans = ilo(point(0, 0), vec.back(), vec[0]);
    return abs(ans) / 2.0;
}

LD count()
{
    LD yy = 0.5;
    for(int i = 0; i < 4; i++)
    {
        if(yy == v[i].y && yy == v[i + 1].y)
        {
            return 0;
        }
    }
    vector < point > my;
    for(int i = 0; i < 4; i++)
    {
        if(v[i].y >= yy) my.push_back(v[i]);
        if(min(v[i].y, v[i + 1].y) <= yy && yy <= max(v[i].y, v[i + 1].y))
        {
            LD xx = (yy - v[i + 1].y) / (v[i].y - v[i + 1].y) * (v[i].x - v[i + 1].x) + v[i + 1].x;
            my.push_back(point(xx, yy));
        }
    }
    return pole(my) * 5.0;
}

int main()
{
    ios_base::sync_with_stdio(0);
    for(int i = 0; i < 4; i++)
    {
        LD x, y; cin >> x >> y;
        v.push_back(point(x, y));
    }
    reverse(all(v));
    v.push_back(v[0]);

    LD ans = 5 * 5 * 5 * 4;
    LD mn[] = {6, 4, 1, 3};
    for(int i = 0; i < 4; i++)
    {
        ans += count() * mn[i];
        rotate();
    }
    cout << fixed << setprecision(15) << ans / 125.0 << "\n";
    return 0;
}