#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int(i) = 0; (i) < (n); (i)++)
#define FOR(i, m, n) for(int(i) = (m); (i) < (n); (i)++)
#define All(v) (v).begin(), (v).end()
#define pb push_back
#define MP(a, b) make_pair((a), (b))
template <class T> vector<T> make_vec(size_t a, T val) {
    return vector<T>(a, val);
}
template <class... Ts> auto make_vec(size_t a, Ts... ts) {
    return vector<decltype(make_vec(ts...))>(a, make_vec(ts...));
}
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using Graph = vector<vector<int>>;
template <typename T> struct edge {
    int to;
    T cost;
    edge(int t, T c) : to(t), cost(c) {}
};
template <typename T> using WGraph = vector<vector<edge<T>>>;
const int INF = 1 << 30;
const ll LINF = 1LL << 60;
const int MOD = 1e9 + 7;

int main() {
    int N;
    cin >> N;
    vector<ll> A(2 * N);
    rep(i, 2 * N) cin >> A[i];
    vector<ll> lcum(N + 1), rcum(N + 1);
    vector<ll> lv(N), rv(N);
    for(int i = 0; i < 2 * N; i += 2) {
        lv[i / 2] = A[i] - A[i + 1];
        rv[i / 2] = A[i + 1] - A[i];
    }
    for(int i = 0; i < N; i++) {
        lcum[i + 1] += lv[i] + lcum[i];
    }
    for(int i = N; i > 0; i--) {
        rcum[i - 1] += rv[i - 1] + rcum[i];
    }
    ll res = -LINF;
    for(int i = 0; i <= N; i++) {
        res = max(res, lcum[i] + rcum[i]);
    }
    cout << res << endl;
}