#include<bits/stdc++.h>
using namespace std;
#define ll long long
ll res;
int main()
{
    ll x1,y1,x2,y2,x3,y3,x4,y4;
    cin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4;
    res=(y2-y1)*(x2-x1)+(y4-y3)*(x4-x3);
    if(min(x2,x4)>max(x1,x3)&&min(y2,y4)>max(y1,y3))
        res-=(min(x2,x4)-max(x1,x3))*(min(y2,y4)-max(y1,y3));
    cout<<res<<endl;
    return 0;
}