struct point
{
    int x,y;
    friend istream& operator>>(istream &in,point &rhs){return in>>rhs.x>>rhs.y;}
};

int main()
{
    point lb[2],rt[2];
    int x,y;
    for(int i=0;i<2;i++)
    {
        cin>>lb[i]>>rt[i];
        if(lb[i].x>rt[i].x)swap(lb[i].x,rt[i].x);
        if(lb[i].y>rt[i].y)swap(lb[i].y,rt[i].y);
    }
    x=abs(max(rt[0].x,rt[1].x)-min(lb[0].x,lb[1].x)-((rt[0].x-lb[0].x)+(rt[1].x-lb[1].x)));
    y=abs(max(rt[0].y,rt[1].y)-min(lb[0].y,lb[1].y)-((rt[0].y-lb[0].y)+(rt[1].y-lb[1].y)));
    if(x<0||y<0)cout<<0<<endl;
    else cout<<x*y<<endl;
    return 0;
}