#include <stdio.h>
#include <stdlib.h>

int min(int a, int b) {
    return (a < b) ? a : b;
}

int max(int a, int b) {
    return (a > b) ? a : b;
}

int solution(int ax1, int ay1, int ax2, int ay2, int bx1, int by1, int bx2, int by2) {
    // Calculate area of first rectangle
    int area1 = (ax2 - ax1) * (ay2 - ay1);
    
    // Calculate area of second rectangle
    int area2 = (bx2 - bx1) * (by2 - by1);
    
    // Check if rectangles overlap
    if (ax2 <= bx1 || bx2 <= ax1 || ay2 <= by1 || by2 <= ay1) {
        return area1 + area2;
    }
    
    // Calculate overlap area
    int overlapWidth = min(ax2, bx2) - max(ax1, bx1);
    int overlapHeight = min(ay2, by2) - max(ay1, by1);
    int overlap = overlapWidth * overlapHeight;
    
    return area1 + area2 - overlap;
}

int main() {
    int ax1, ay1, ax2, ay2, bx1, by1, bx2, by2;
    scanf("%d", &ax1);
    scanf("%d", &ay1);
    scanf("%d", &ax2);
    scanf("%d", &ay2);
    scanf("%d", &bx1);
    scanf("%d", &by1);
    scanf("%d", &bx2);
    scanf("%d", &by2);
    
    printf("%d\n", solution(ax1, ay1, ax2, ay2, bx1, by1, bx2, by2));
    
    return 0;
}