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

int main(){
  int N;
  cin >> N;
  vector<int> A(2*N);
  for(auto &a : A) cin >> a;
  vector<long long> L(N+1), R(N+1);
  for(int i = 0; i < N; ++i){
    L[i+1] = L[i] + A[2*i] - A[2*i+1];
    R[i+1] = R[i] + A[2*N-2*i-1] - A[2*N-2-2*i];
  }
  long long ans = 0;
  for(int i = 0; i <= N; ++i){
    ans = max(ans,L[i]+R[N-i]);
  }
  cout << ans << endl;
}