#include <bits/stdc++.h>
#define rep(i,n) for (ll i = 0; i < n; ++i)
#define sz(x) int(x.size())
#define ALL(c) (c).begin(), (c).end()
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v, x) (std::find(v.begin(), v.end(), x) != v.end())
#define FORV(i, v) for (auto i = v.begin(); i != v.end(); i++)
using namespace std;

typedef long long ll;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
const int INF = 1001001001;
const long long INFL = (1LL<<60);
const double eps = (1e-9);

ll calc(ll x) {
  ll ret = 0;
  while (x != 0) {
    ret += x % 10;
    x /= 10;
  }
  return ret;
}

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

  int n;
  cin >> n;
  vector<ll> a(2 * n);
  rep(i, 2 * n) cin >> a[i];

  vector<ll> l(n);
  vector<ll> r(n);

  rep(i, n) {
    l[i] = a[2 * i] - a[2 * i + 1];
  }

  for (int i = n - 1; i >= 0; i--) {
    r[i] = a[2*i + 1] - a[2 * i];
  }

  vector<ll> ls(n);
  vector<ll> rs(n);
  ls[0] = l[0];
  rs[n-1] = r[n-1];
  for (int i = 1; i < n; i++) {
    ls[i] = ls[i-1] + l[i];
  }
  for (int i = n - 2; i >= 0; i--) {
    rs[i] = rs[i+1] + r[i];
  }

  ll ans = max(ls[n-1], rs[0]);

  rep(i, n-1) {
    chmax(ans, ls[i] + rs[i+1]);
  }

  cout << ans << endl;

  return 0;
}