#include <iostream>
#include <algorithm>
#include <cstdio>
using namespace std;
int main() {
int n, minx, miny, maxx, maxy;
cin >> n >> minx >> miny >> maxx >> maxy;
for (int i = 1; i < n; i++) {
int minxa, minya, maxxa, maxya;
cin >> minxa >> minya >> maxxa >> maxya;
minx = max(minx, minxa);
miny = max(miny, minya);
maxx = min(maxx, maxxa);
maxy = min(maxy, maxya);
}
cout << (int64_t)max(0, maxx - minx) * max(0, maxy - miny) << endl;
}
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