#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < (int)(n); ++i)
#define all(x) x.begin(),x.end()
#define ln '\n'
const long double PI = acos(-1.0L);
const long long MOD = 1000000007LL;
// const long long MOD = 998244353LL;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
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; }
//////////////////////////////////////////////////////////////////////////////////////////////////////////

int main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);
    int N; cin >> N;
    vector<ll> A(2*N);
    rep(i,2*N) cin >> A[i];

    vector<ll> B(N+1),C(N+1);
    rep(i,N) {
        B[i+1] = A[2*i] - A[2*i+1];
        B[i+1] += B[i];
    }
    reverse(all(A));
    rep(i,N) {
        C[i+1] = A[2*i] - A[2*i+1];
        C[i+1] += C[i];
    }
    reverse(all(A));
    reverse(all(C));
    ll ans = 0;
    rep(i,N+1) {
        chmax(ans,B[i]+C[i]);
    }

    cout << ans << ln;
}