#include <bits/stdc++.h>
using namespace std;

int main() {
    ios_base::sync_with_stdio(false); cin.tie(NULL);
    int n; cin >> n;
    vector<pair<long long, long long>> segs(n);
    for (int i = 0; i < n; i++)
        cin >> segs[i].first >> segs[i].second;
    sort(segs.begin(), segs.end());
    long long curL = segs[0].first, curR = segs[0].second;
    long long ans = 0;
    for (int i = 1; i < n; i++) {
        if (segs[i].first <= curR) {
            curR = max(curR, segs[i].second);
        } else {
            ans = max(ans, segs[i].first - curR);
            curL = segs[i].first;
            curR = segs[i].second;
        }
    }
    cout << ans << "\n";
    return 0;
}