#include <iostream>
using namespace std;
const int N = 110;

int n, a, b, c, d;

int main()
{
	while (cin >> n)
	{
		int cnt = 0;
		bool pic[N][N] = {false};
		for (int k = 0; k < n; k ++ )
		{
			cin >> a >> b >> c >> d;
			for (int i = a; i < c; i ++ )
				for (int j = b; j < d; j ++ )
					pic[i][j] = true;
		}
		for (int i = 0; i <= 100; i ++ )
			for (int j = 0; j <= 100; j ++ )
				if (pic[i][j]) cnt ++;
		cout << cnt << endl;
	}
	return 0;
}