#include <iostream>
#include <vector>
using namespace std;

int main()
{
    int N;
    cin >> N;
    int a[N];
    for (int i = 0;i < N;++i)
        cin >> a[i];
    int i = 0, j = N - 1,sum = 0;
    while (i <= j)
    {
        if (a[i] == a[j])
        {
            if (i < j)
            {
                sum += (a[i] + a[j]);
                ++i;
                --j;
            }
            else if (i == j)
            {
                sum += a[i];
                break;
            }
        }
        else
        {
            if (a[i] < a[j])
            {
                sum += (2 * a[i]);
                ++i;
            }
            else
            {
                sum += (2 * a[j]);
                --j;
            }
        }
    }
    cout << sum<< endl;
    return 0;
}