#include <iostream>
#include <vector>
using namespace std;
int main() {
    int n;
    cin >> n;
    vector<int> x1;
    vector<int> x2;
    for (int i = 0; i < n; i++) {
        int z;
        cin >> z;
        x1.push_back(z);
        cin >> z;
        x2.push_back(z);
    }
    int s1, s2;
    s1 = x1[0];
    s2 = x2[0];
    for (int i = 1; i < n; i++) {
        if (s1 < x1[i]) {
            s1 = x1[i];
        }
        if (s2 > x2[i]) {
            s2 = x2[i];
        }
    }
    if (s2 - s1 < 0) {
        cout << 0;
    }
    else cout << s2 - s1;
    return 0;
}