#include <iostream> #include <algorithm> using namespace std; int main() { int N; int x1[500] = { 0 }, y1[500] = { 0 }, x2[500] = { 0 }, y2[500] = { 0 }; int sum = 0; cin >> N; for (int i = 0; i < N; i++) { cin >> x1[i] >> y1[i]>>x2[i]>>y2[i]; sum += ((x2[i] - x1[i]) * (y2[i] - y1[i])); } for (int i = 1; i < N; i++) { for (int j = 0; j < i; j++) { if (x1[i] >= x1[j] && x1[i] <= x2[j]) { sum -= (min(x2[i], x2[j]) - x1[i]) * (min(y2[i], y2[j]) - max(y1[i], y1[j])); } else if (x1[j] >= x1[i] && x1[j] <= x2[i]) { sum -= (min(x2[i], x2[j]) - x1[i]) * (min(y2[i], y2[j]) - max(y1[i], y1[j])); } } } cout << sum; return 0; }