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

int main(){
    ll x1,y1,x2,y2,x3,y3,x4,y4;
    cin>>x1>>y1;
    cin>>x2>>y2;
    cin>>x3>>y3;
    cin>>x4>>y4;
    ll x_left=max(x1,x3);
    ll y_bottom=max(y2,y4);
    ll x_right=min(x2,x4);
    ll y_top=min(y1,y3);
    ll x=x_right-x_left;
    ll y=y_top-y_bottom;
    ll s=0;
    //meothinhle
    if (x>0 && y>0){
        s=x*y;
    };
    cout<<s;
    return 0;
}