#include <bits/stdc++.h>
using namespace std;
#define MAXN 100000
const int inf = 2147483647;
long long n,max_x = -inf,max_y = -inf,min_x = inf,min_y = inf,xx1,yy1,xx2,yy2,ans;
int main(){
	cin >> n;
	for(int i = 1;i <= n;i++){
		cin >> xx1 >> yy1 >> xx2 >> yy2;
		max_x = max(xx2,max_x);
		min_x = min(xx1,min_x);
		max_y = max(yy2,max_y);
		min_y = min(yy1,min_y);
	}
    ans = (max_x - min_x) * (max_y - min_y);
	cout << ans << endl;
	return 0;
}