#include <bits/stdc++.h>
using namespace std;
 
 
int main() {
    int n;
    cin >> n;
    vector<pair<long long, long long>> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i].first >> a[i].second;
    }
    sort(a.begin(), a.end());// Sắp xếp theo thời gian bắt đầu
 
    long long maxlength = 0;
    long long xt = a[0].first, yt = a[0].second;
    for (int i = 1; i < n; i++) {
        long long x = a[i].first, y = a[i].second;
        if(x <= yt){ // thỏa mãn để nối
            yt = max(yt, y); // lấy kết thúc dài hơn
        } else { // kiểm tra khi không nối được
            maxlength = max(maxlength, yt - xt);
            xt = x;
            yt = y;
        }
    }
    maxlength = max(maxlength, yt - xt); // kiểm tra đoạn cuối cùng
 
    cout << maxlength << endl;
    return 0;
}

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