#include <cstdio>
#include <algorithm>
using namespace std;

int main()
  {
   int pL,pT,pR,pB,qL,qT,qR,qB;
   scanf("%d%d%d%d%d%d%d%d",&pL,&pT,&pR,&pB,&qL,&qT,&qR,&qB);
   int p = (pR - pL) * (pB - pT)
   int q = (qR - qL) * (qB - qT)
   int distanceR = min(pR, qR);
   int distanceL = max(pL, qL);
   int distanceRL = max(0, distanceR- distanceL);
   int distanceB = min(pB, qB);
   int distanceT = max(pT, qT);
   int distanceBT = max(0, distanceB - distanceT);
   int result = p + q - distanceRL * distanceBT;
   printf("%d\n", result);
   return 0;
  }