#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int,int>;
constexpr ll INF = 9e18;
constexpr int inf = 1e9;
const double INFD = 1e100;
const ll mod = 1000000007;
const double PI = 3.1415926535897932384626433832795028841971;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
};
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
};

// intやllをstringに変換
template<typename T> inline string toString(const T &a){
  ostringstream oss;
  oss << a;
  return oss.str();
};
// ----------------------------------------------------------------------------

int main(){
  int N;
  cin >> N;
  vector<ll> A(N*2);
  for(int i=0; i<N*2; i++){
    cin >> A[i];
  }
  vector<ll> S(N+1,0),R(N+1,0);
  int l = 0;
  for(int i=0; i<N; i++){
    S[i+1] = S[i] + A[l] - A[l+1];
    l += 2;
  }
  int r = N*2 - 1;
  for(int i=N; i>0; i--){
    R[i-1] = R[i] + A[r] - A[r-1];
    r -= 2;
  }
  ll ans = 0;
  for(int i=0; i<=N; i++){
    ll res = 0;
    res += S[i] + R[i];
    chmax(ans, res);
  }
  cout << ans << endl;
  return 0;
}