#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
int main() {
	cin.tie(0);
	ios_base::sync_with_stdio(false);
	int N;
	cin >> N;
	vector<int> A(2 * N);
	for (int i = 0; i < 2 * N; ++i) {
		cin >> A[i];
	}
	vector<long long> ldp(N + 1), rdp(N + 1);
	for (int i = 0; i < N; ++i) {
		ldp[i + 1] = ldp[i] + A[2 * i] - A[2 * i + 1];
	}
	for (int i = N - 1; i >= 0; --i) {
		rdp[i] = rdp[i + 1] + A[2 * i + 1] - A[2 * i];
	}
	long long ans = 0;
	for (int i = 0; i < N; ++i) {
		ans = max(ans, ldp[i] + rdp[i]);
	}
	cout << ans << endl;
	return 0;
}