#include <iostream>

using namespace std;

long long wb(long long c)
{
    if(c<0) return -c;
    else return c;
}
int main()
{
    long long x1,y1,x2,y2,x3,y3,x4,y4,x,y,xx,yy;
    cin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4;
    x = max(x1,x3);
    y = min(y1,y3);
    xx = min(x2,x4);
    yy = max(y2,y4);
    cout<<wb((x-xx)*(y-yy));
    return 0;
}