#pragma GCC optimize("Ofast", "unroll-loops")

#include <bits/stdc++.h>

using namespace std;

#define ll long long

int main() {
	int N; cin >> N;
	vector<int> d(N);
	for (int i = 0; i < N; ++i) {
		int al, ar; cin >> al >> ar;
		d[i] = al - ar;
	}
	// dのtotalを計算
	ll total = 0;
	for (auto di : d) total += di;
	// 答えの計算
	ll res = -total;
	ll tmp = 0;
	for (int i = 0; i < N; ++i) {
		tmp += d[i];
		res = max(res, tmp - (total - tmp));
	}
	cout << res << endl;
	return 0;
}