#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <ctype.h>
#include <string.h>
#pragma warning(disable:4996)
typedef long long LL, s64;
typedef unsigned long long ULL, u64;
#define MIN(x,y) (((x)>(y))?(y):(x))
#define MAX(x,y) (((x)>(y))?(x):(y))
int main(){
    LL a, b, c, d, e, f, g, h;
    scanf("%lld%lld%lld%lld%lld%lld%lld%lld", &a, &b, &c, &d, &e, &f, &g, &h);
    if((MIN(c, g) > MAX(a, e)) && (MIN(d, h) > MAX(b, f))){
        printf("%lld\n", (MIN(c, g) - MAX(a, e)) * (MIN(d, h) - MAX(b, f)));
    }
    else{
        puts("0");
    }
    return 0;
}