#include <bits/stdc++.h>
#define int long long 
using namespace std;
using Graph = vector<vector<int>>;

signed main(){
  int N;
  cin >> N;
  vector<int> A(2*N);
  for( int i = 0; i < 2*N; i++ ) cin >> A.at(i);
  
  vector<int> right(N);
  vector<int> left(N);
  for( int i = 0; i < N; i++ ){
    left.at(i) = A.at(i*2)-A.at(i*2+1);
    if( i > 0 ) left.at(i) += left.at(i-1);
  }
  reverse(A.begin(), A.end());
  for( int i = 0; i < N; i++ ){
    right.at(i) = A.at(i*2)-A.at(i*2+1);
    if( i > 0 ) right.at(i) += right.at(i-1);
  }
  reverse(right.begin(), right.end());
  
  /* for( int i = 0; i < N; i++ ) cout << left.at(i) << " ";
  cout << endl;
  for( int i = 0; i < N; i++ ) cout << right.at(i) << " ";
  cout << endl; */
  
  //全部右からとった場合、全部左からとった場合
  int ans = max(left.at(N-1), right.at(0));
  
  for( int i = 0; i < N-1; i++ ){
    int now = left.at(i)+right.at(i+1);
    ans = max(ans, now);
  }
  cout << ans << endl;
    
}