#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

int main(void) {
    int n;
    cin >> n;

    vector<long long> a(2 * n);
    vector<long long> x(n+1, 0), y(n+1, 0);

    for (int i = 0; i < 2 * n; ++i) cin >> a[i];

    for (int i = 0; i < 2 * n; i += 2) x[i / 2 + 1] += x[i / 2] + a[i] - a[i+1];

    reverse(a.begin(), a.end());

    for (int i = 0; i < 2 * n; i += 2) y[i / 2 + 1] += y[i / 2] + a[i] - a[i+1];

    long long ans = 0;
    for (int i = 0; i <= n; ++i) {
        ans = max(ans, x[i] + y[n - i]);
    }

    cout << ans << endl;
}