#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
template <typename T> using posteriority_queue = priority_queue<T, vector<T>, greater<T> >;
const int INF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3fLL;
const double EPS = 1e-8;
const int MOD = 1000000007;
// const int MOD = 998244353;
const int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
const int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
template <typename T> void unique(vector<T> &a) { a.erase(unique(ALL(a)), a.end()); }
struct IOSetup {
  IOSetup() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int n; cin >> n;
  vector<int> a(n * 2); REP(i, n * 2) cin >> a[i];
  vector<ll> l(n, 0), r(n, 0);
  REP(i, n) {
    l[i] = a[i * 2] - a[i * 2 + 1];
    if (i > 0) l[i] += l[i - 1];
  }
  for (int i = n - 1; i >= 0; --i) {
    r[i] = a[i * 2 + 1] - a[i * 2];
    if (i + 1 < n) r[i] += r[i + 1];
  }
  ll ans = r[0];
  REP(i, n) chmax(ans, l[i] + (i + 1 < n ? r[i + 1] : 0));
  cout << ans << '\n';
  return 0;
}