#include <iostream>
using namespace std;

int main() {
  freopen("square.in", "r", stdin);
  freopen("square.in", "w", stdout);

  int x1, y1, x2, y2;
  cin >> x1, y1, x2, y2;
  int a1, b1, a2, b2;
  cin >> a1, b1, a2, b2;

  int min_x, min_y, max_x, max_y;
  min_x = min(min(x1, x2), min(a1, a2));
  min_y = min(min(y1, y2), min(b1, b2));
  max_x = max(min(x1, x2), min(a1, a2));
  max_y = max(min(y1, y2), min(b1, b2));

  int x_len = max_x - min_x;
  int y_len = max_y - min_y;

  cout << x_len * y_len << endl;
}