#include <iostream>
#include <vector>
using namespace std;

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

  int N; cin >> N;
  int N2 = N * 2;
  vector<long long> A(N2);
  for (int i = 0; i < N2; i++) cin >> A[i];
  vector<long long> cs1(N2+1), cs2(N2+1);
  for (int i = 0; i < N; i++) {
    cs1[i+1] = cs1[i] + A[i*2] - A[i*2+1];
    cs2[i+1] = cs2[i] + A[N2-i*2-1] - A[N2-i*2-2];
  }
  long long ans = 0;
  for (int i = 0; i <= N; i++) {
    ans = max(ans, cs1[i] + cs2[N-i]);
  }
  cout << ans << "\n";
}