#include <algorithm>
#include <iostream>
#include <utility>
#include <vector>
using namespace std;

bool comp(const pair<int, int> a, const pair<int, int> b) {
	return 2 * a.first - a.second > 2 * b.first - b.second;
}

int main() {
	int ans = 0;
	size_t N;
	cin >> N;
	vector<pair<int, int>> AB(N);
	for (size_t i = 0; i < N; ++i) cin >> AB[i].first >> AB[i].second;
	sort(AB.begin(), AB.end(), comp);
	for (size_t i = 1; i < N; ++i) ans = max(ans, AB[i - 1].second - AB[i - 1].first + AB[i].first);
	cout << ans;
}