#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using PII = pair<ll, ll>;
#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
template<typename T> void chmin(T &a, const T &b) { a = min(a, b); }
template<typename T> void chmax(T &a, const T &b) { a = max(a, b); }
struct FastIO {FastIO() { cin.tie(0); ios::sync_with_stdio(0); }}fastiofastio;
#ifdef DEBUG_ 
#include "../program_contest_library/memo/dump.hpp"
#else
#define dump(...)
#endif
const ll INF = 1LL<<60;

int main(void) {
    ll n;
    cin >> n;
    vector<ll> a(2*n);
    REP(i, 2*n) cin >> a[i];

    vector<ll> vl(n);
    REP(i, n) vl[i] = (i==0?0:vl[i-1]) + a[2*i] - a[2*i+1];
    vector<ll> vr(n);
    for(ll i=n-1; i>=0; --i) vr[i] = (i==n-1?0:vr[i+1]) + a[2*i+1] - a[2*i];
    dump(vl);
    dump(vr);

    ll ret = -INF;
    chmax(ret, vl[n-1]);
    chmax(ret, vr[0]);
    REP(i, n-1) chmax(ret, vl[i] + vr[i+1]); 
    cout << ret << endl;

    return 0;
}