#include <bits/stdc++.h>
using namespace std;
using lint     = long long;
const lint inf = 1LL << 60;
const lint mod = 1000000007;

template <class T>
bool chmax(T &a, const T &b) {
    return (a < b) ? (a = b, 1) : 0;
}
template <class T>
bool chmin(T &a, const T &b) {
    return (b < a) ? (a = b, 1) : 0;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    lint n;
    cin >> n;
    vector<lint> a(2 * n);
    for (int i = 0; i < 2 * n; ++i) {
        cin >> a[i];
    }
    vector<lint> b(n, 0), c(n, 0);
    for (int i = 0; i < n; ++i) {
        b[i] = a[2 * i] - a[2 * i + 1];  // left - right
        c[i] = -a[2 * i] + a[2 * i + 1]; // right - left
    }
    for (int i = 1; i < n; ++i) {
        b[i] += b[i - 1];
        c[i] += c[i - 1];
    }
    lint ret = c[n - 1];
    // lint k   = (n + 1) / 2;
    // lint ret = tot - 2 * (a[n] - a[n - k]);
    for (int i = 0; i < n; ++i) {
        lint temp = c[n - 1] + 2 * b[i];
        chmax(ret, temp);
    }
    cout << ret << "\n";
    return 0;
}