#include <iostream>
#include <algorithm>
#define x first
#define y second
using namespace std;
typedef pair<int, int> PII;
const int N = 2010;
int n;
PII p[N], q[N];
int get(PII a, PII b)
{
    if (a.y < b.x || b.y < a.x) return 0;
    return min(a.y, b.y) - max(a.x, b.x);
}
int main()
{
    cin >> n;
    for (int i = 0; i < n; i ++ ) cin >> p[i].x >> p[i].y;
    for (int i = 0; i < n; i ++ ) cin >> q[i].x >> q[i].y;
    int res = 0;
    for (int i = 0; i < n; i ++ )
        for (int j = 0; j < n; j ++ )
            res += get(p[i], q[j]);
    cout << res << endl;
    return 0;
}