#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
// Welcome to my source code!

int main() {
    int n;
    cin >> n;
    n *= 2;
    ll a[n], sum = 0;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
        sum += a[i];
    }
    ll al[n + 1], ar[n + 1];
    al[0] = 0, ar[n] = 0;
    for (int i = 1; i <= n; i++) {
        if (i & 1) al[i] = al[i - 1] + a[i - 1];
        else al[i] = al[i - 1];
    }
    for (int i = n - 1, t = (n - 1) % 2; i >= 0; i--) {
        if (i & t) ar[i] = ar[i + 1] + a[i];
        else ar[i] = ar[i + 1];
    }
    ll ans = 0;
    for (int i = 0; i < n; i++) {
        ll t = al[i] + ar[i + 1];
        ans = max(ans, t - (sum - t));
    }
    cout << ans << endl;
}