#include <iostream>
using namespace std;
const int N = 110;
bool d[N][N];

int main() {
    int n, ans = 0; 
    cin >> n;
    for (int i = 0; i < n; i++) {
        int x1, y1, x2, y2;
        cin >> x1 >> y1 >> x2 >> y2;
        for (int x = x1; x < x2; x++) {
            for (int y = y1; y < y2; y++) {
                if (!d[x][y]) {
                    ans++;
                    d[x][y] = true;
                }
            }
        }
    }
    cout << ans << endl;
    return 0;
}