#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define repr(i, n) for (int i = (n) - 1; i >= 0; i--)
#define range(a) a.begin(), a.end()

int main() {
  int n;
  cin >> n;
  n *= 2;
  vector<ll> a(n);
  ll total = 0;
  rep(i, n) {
    cin >> a[i];
    total += a[i];
  }
  vector<ll> even_pref(n + 1);
  for (int i = 0; i + 2 <= n; i += 2) {
    even_pref[i + 2] = even_pref[i] + a[i + 1];
  }
  vector<ll> even_suff(n + 1);
  for (int i = n; i - 2 >= 0; i -= 2) {
    even_suff[i - 2] = even_suff[i] + a[i - 2];
  }
  ll ans = LLONG_MAX;
  for (int i = 0; i <= n; i += 2) {
    ans = min(ans, even_pref[i] + even_suff[i]);
  }
  cout << total - (ans * 2) << endl;
}