#include <algorithm>
#include <iostream>
#include <queue>
using namespace std;
typedef long long ll;
typedef pair<int, int> P;

int main()
{
    int n;
    cin >> n;
    P p[200005];
    for (int i = 0; i < n; i++)
    {
        cin >> p[i].first >> p[i].second;
    }
    int l = 0;
    sort(p, p + n);
    for (int i = 0; i < n; i++)
    {
        l = max(l, p[i].first - (i + 1));
    }
    for (int i = 0; i < n; i++)
    {
        swap(p[i].first, p[i].second);
    }
    int r = 2000000000;
    sort(p, p + n);
    for (int i = 0; i < n; i++)
    {
        r = min(r, p[i].first - (i + 1));
    }
    cout << max(0, r - l + 1) << endl;
}