#include <iostream>
#include <algorithm>
#define rep(i, n) for(i = 0; i < n; i++)
#define int long long
using namespace std;

int n;
int a[200000];
int head[100001];
int tail[100001];

signed main() {
	int i;
	
	cin >> n;
	rep(i, 2 * n) cin >> a[i];
	
	rep(i, n) {
		head[i + 1] = head[i] + a[2 * i] - a[2 * i + 1];
	}
	rep(i, n) {
		tail[i + 1] = tail[i] + a[2 * n - 1 - 2 * i] - a[2 * n - 1 - 2 * i - 1];
	}
	
	int ans = -1e+15;
	rep(i, n + 1) {
		int res = head[i] + tail[n - i];
		ans = max(ans, res);
	}
	cout << ans << endl;
	return 0;
}