#include<iostream>
#include<algorithm>
#include<vector>
#include<functional>
#include<string>
#include<cmath>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<cstdio>
using namespace std;
using ll = long long;
int main(){
  int n;
  cin >> n;
  vector<int> a(2 * n);
  for (int i = 0; i < 2 * n; i++){
    cin >> a[i];
  }
  int left = 0, right = 2 * n - 1;

  vector<ll> sum1(n + 5, 0), sum2(n + 5, 0);

  for (int i = 0; i < n; i++){
    sum1[i + 1] = sum1[i] + a[2 * i] - a[2 * i + 1];
    //cout << sum1[i + 1] << " ";
  }
  //cout << endl;
  for (int i = 0; i < n; i++){
    sum2[i + 1] = sum2[i] + a[ 2 * n - 2 * i - 1] - a[ 2 * n - 2 * i - 2];
    //cout << sum2[i + 1] << " ";
  }
  //cout << endl;

  ll sum = sum1[n] + sum2[n];

  ll ans = 0;
  for (int i = 0; i <= n; i++){
    ans = max(ans, sum1[i] + sum2[n-i]);
  }
  //cout << endl << sum << " ";

  cout << ans << "\n";
  return 0;
}