#include <iostream>

using namespace std;

const int N = 110;

bool m[N][N];

int main() {
    int T;
    cin >> T;

    int a,b,c,d;
    while (T--) {
        cin >> a >> b >> c >> d;
        for (int i = a; i < c; ++i) {
            for (int j = b; j < d; ++j) {
                m[i][j] = true;
            }
        }
    }

    int res = 0;
    for (int i=0; i< N; ++i) {
        for (int j = 0; j < N; ++j) {
            res += m[i][j];
        }
    }

    cout << res << endl;

    return 0;
}