#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int main() {
    ll n;
    cin >> n;
    n *= 2;
    ll a[n];
    for (int i = 0; i < n; i++)
    {
        cin >> a[i];
    }
    
    ll sum = 0;
    for (int i = 0; i < n; i++)
    {
        sum += a[i];
    }
    
    ll sumL[n/2];
    ll sumR[n/2];
    memset(sumL, 0, sizeof(sumL));
    memset(sumR, 0, sizeof(sumR));
    sumL[0] = a[0];
    for (int i = 2; i < n; i+=2)
    {
        sumL[i/2] = a[i] + sumL[i/2-1];
    }
    sumR[n/2-1] = a[n-1];
    for (int i = n-3; i >= 0; i-=2)
    {
        sumR[i/2] = a[i] + sumR[i/2+1];
    }
    
    ll ans = max(sumL[n/2-1]-sumR[0], sumR[0]-sumL[n/2-1]);
    for (int i = 0; i < n/2-1; i++)
    {
        ans = max(ans, 2*(sumL[i]+sumR[i+1])-sum);
    }
    
    cout << ans << endl;

    return 0;
}