// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC target ("avx,avx2,fma")
#include <bits/stdc++.h>

using std::cin, std::cout, std::cerr;
using ll = long long;

int main() {
    std::ios::sync_with_stdio(false);
    int n; cin >> n;
    std::vector<ll> f(2 * n + 2), g(2 * n + 2);
    std::vector<ll> a(2 * n + 1);
    for(int i = 1; i <= 2 * n; i ++)
        cin >> a[i];
    for(int i = 2; i <= 2 * n; i += 2)
        f[i] = f[i - 2] + a[i - 1] - a[i];
    for(int i = 2 * n - 1; i >= 1; i -= 2)
        g[i] = g[i + 2] + a[i + 1] - a[i];

    ll ans = -1e18L;
    for(int i = 0; i <= 2 * n; i += 2)
        ans = std::max(ans, f[i] + g[i + 1]);
    cout << ans << '\n';
}