#include <iostream>

using namespace std;

const int N = 110;

int n;
bool st[N][N];                      //整一个布尔矩阵存涂了颜色的区块

int main()
{
    cin >> n;
    while (n -- )
    {
        int x1, y1, x2, y2;
        cin >> x1 >> y1 >> x2 >> y2;

        for (int i = x1; i < x2; i ++ )
            for (int j = y1; j < y2; j ++ )
                st[i][j] = true;    //涂了就true，重复涂也不会影响
    }

    int res = 0;
    for (int i = 0; i < N; i ++ )
        for (int j = 0; j < N; j ++ )
            res += st[i][j];        //统计一下总共多少涂颜色的块

    cout << res << endl;

    return 0;
}