#include <bits/stdc++.h>
using namespace std;
const int N = 1e4 + 10;
int n, sum;
bool p[N][N];
/*
2
2 2 9 5
6 1 12 9
*/
void paint(int x1, int y1, int x2, int y2) {
    for (int i = x1; i < x2; i++)
        for (int j = y1; j < y2; j++)
            p[i][j] = 1;
}
int main() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
        int x1, y1, x2, y2;
        cin >> x1 >> y1 >> x2 >> y2;
        paint(x1, y1, x2, y2);
    }
    for (int i = 0; i < N; i++)
        for (int j = 0; j < N; j++)
            if (p[i][j]) sum++;

    printf("%d\n", sum);
    return 0;
}