#include <bits/stdc++.h>
#define rep(i,n) for(int i=(0);i<(n);i++)

using namespace std;

typedef long long ll;

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int n;
	cin >> n;

	vector<ll> a(2 * n);
	rep(i, 2 * n) cin >> a[i];

	vector<ll> elcum(n+1, 0), ercum(n+1, 0);
	vector<ll> olcum(n+1, 0), orcum(n+1, 0);
	rep(i, n){
		elcum[i + 1] = elcum[i] + a[2 * i]; 
		olcum[i + 1] = olcum[i] + a[2 * i + 1];
	}

	for(int i = n - 1; i >= 0; i--){
		ercum[i] = ercum[i+1] + a[2 * i];
		orcum[i] = orcum[i+1] + a[2 * i + 1];
	}

	ll ans = 0;
	rep(i, n){
		ans = max(ans, elcum[i] + orcum[i] - (olcum[i] + ercum[i]));
		ans = max(ans, olcum[i] + ercum[i] - (elcum[i] + orcum[i]));
	}

	cout << ans << endl;
}