#include <bits/stdc++.h>  // clang-format off
using namespace std;
using Int = long long;
#define REP2(i, n) for (Int i = 0, max_i = (n); i < max_i; i++)
#define REP3(i, a, b) for (Int i = (a), max_i = (b); i < max_i; i++)
#define OVERLOAD2(_1, _2, _3, name, ...) name
#define REP(...) OVERLOAD2(__VA_ARGS__, REP3, REP2)(__VA_ARGS__)
struct SetupIO { SetupIO() { cin.tie(nullptr), ios::sync_with_stdio(false), cout << fixed << setprecision(13); } } setup_io;
#ifndef _MY_DEBUG
#define dump(...)
#endif  // clang-format on

/**
 *    author:  knshnb
 *    created: Fri Feb 28 21:23:06 JST 2020
 **/

template <class T> inline bool chmin(T& a, const T& b) {
    if (a <= b) return false;
    a = b;
    return true;
}
template <class T> inline bool chmax(T& a, const T& b) {
    if (a >= b) return false;
    a = b;
    return true;
}

signed main() {
    Int n;
    cin >> n;
    vector<Int> a(2 * n);
    REP(i, 2 * n) cin >> a[i];
    vector<Int> odd(n + 1), even(n + 1);
    REP(i, n) {
        even[i + 1] = even[i] + a[2 * i];
        odd[i + 1] = odd[i] + a[2 * i + 1];
    }
    Int ans = 0;
    REP(i, n + 1) {
        Int l = even[i] - odd[i];
        Int r = (odd[n] - odd[i]) - (even[n] - even[i]);
        chmax(ans, l + r);
    }
    cout << ans << endl;
}