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

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

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

int computeArea(int ax1, int ay1, int ax2, int ay2, 
               int bx1, int by1, int bx2, int by2) {
    // Calculate area of rectangle A
    int areaA = (ax2 - ax1) * (ay2 - ay1);
    
    // Calculate area of rectangle B
    int areaB = (bx2 - bx1) * (by2 - by1);
    
    // Find intersection boundaries
    int left = max(ax1, bx1);
    int right = min(ax2, bx2);
    int bottom = max(ay1, by1);
    int top = min(ay2, by2);
    
    // Calculate overlap area (0 if no overlap)
    int overlap = 0;
    if (left < right && bottom < top) {
        overlap = (right - left) * (top - bottom);
    }
    
    return areaA + areaB - overlap;
}

int main() {
    int coords[8];
    for (int i = 0; i < 8; i++) {
        scanf("%d", &coords[i]);
    }
    
    int result = computeArea(coords[0], coords[1], coords[2], coords[3],
                           coords[4], coords[5], coords[6], coords[7]);
    printf("%d\n", result);
    
    return 0;
}