#include <iostream>
#define x first
#define y second
using namespace std;
typedef pair<int, int> pii;
typedef long long ll;
const int N = 2e3 + 10;
pii a[N], b[N];
ll cmp(int i, int j){
    if(a[i].x <= b[j].x && b[j].x <= a[i].y)    return min(a[i].y, b[j].y) - b[j].x;
    else if(a[i].x >= b[j].x && a[i].x <= b[j].y)   return min(b[j].y, a[i].y) - a[i].x;
    return 0;
}
int main(){
    int n;  cin >> n;
    for(int i = 0; i < n; i ++ )    cin >> a[i].x >> a[i].y;
    for(int i = 0; i < n; i ++ )    cin >> b[i].x >> b[i].y;
    ll res = 0;
    for(int i = 0; i < n; i ++ )
        for(int j = 0; j <= n; j ++ )
            res += cmp(i, j);
    cout << res << endl;
    return 0;
}