#include <iostream>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>
#include <math.h>
#include <map>
#include <set>
#include <queue>

using namespace std;
typedef long long ll;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    int ind = 0;
    vector <pair<int, bool>> a(n * 2);
    for (int i = 0; i < n; i++) {
        int x, y;
        cin >> x >> y;
        a[ind++] = { x, true };
        a[ind++] = { y, false };
    }

    sort(a.begin(), a.end());

    int ans = 0;

    int count = 1;
    for (int i = 1; i < a.size(); i++) {
        if (count >= 1)
            ans += a[i].first - a[i - 1].first;
        if (a[i].second == true)
            count++;
        else
            count--;

    }

    cout << ans;
    return 0;
}