#include <bits/stdc++.h>

using namespace std;

//矩形结构体
struct rec {
    int x1, y1, x2, y2;
};


int main() {
    int n;
    cin >> n;
    //利用set去重
    set<pair<int, int>> _set;

    for (int i = 0; i < n; i++) {
        int x1, y1, x2, y2;
        cin >> x1 >> y1 >> x2 >> y2;

        int count = 0;
        for (int j = x1; j < x2; j++) {
            for (int k = y1; k < y2; k++) {
                rec s;
                s.x1 = j;
                s.x2 = j + 1;

                s.y1 = k;
                s.y2 = k + 1;
                _set.insert(make_pair(s.x1,s.y1));
                count++;
            }
        }
//        cout << "count=" << count << endl;
    }
    cout << _set.size() << endl;
    return 0;
}

/*
struct rec {
    int x1;
    int x2;
    int y1;
    int y2;
} a[100];

int main() {
    int n, i, j, k, f[100][100] = {0};
    int s = 0;

    cin >> n;
    for (i = 0; i < n; i++) {
        int count=0;

        cin >> a[i].x1 >> a[i].y1 >> a[i].x2 >> a[i].y2;
        for (j = a[i].x1; j < a[i].x2; j++)
            for (k = a[i].y1; k < a[i].y2; k++) {
                f[j][k] = 1;
                count++;
            }

        cout<<"count="<<count<<endl;
    }
    for (i = 0; i < 100; i++)
        for (j = 0; j < 100; j++) {
            if (f[i][j] == 1) s++;
        }
    cout << s << endl;
    return 0;
}
*/