#include "bits/stdc++.h"
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
 
typedef long long ll;

int main() {
    int N;
    cin >> N;
    vector<ll> A(2 * N), L(N + 1, 0), R(N + 1, 0);
    rep(i, 2 * N) cin >> A[i];
    rep(i, N) L[i + 1] = L[i] + A[2 * i] - A[2 * i + 1];
    rep(i, N) R[N - 1 - i] = R[N - i] + A[2 * N - 1 - 2 * i] - A[2 * N - 2 - 2 * i];
    ll ans = -1e18;
    rep(i, N + 1) {
        ll s = L[i] + R[i];
        if (s > ans) ans = s;
    }
    cout << ans << endl;
    /*
    rep(i, N + 1) {
        cout << L[i] << " " << R[i] << endl;
    }
    */
}