#include <algorithm>
#include <cstdio>
#include <vector>
 
using namespace std;
 
const int Nmax = 100005;
 
int Values[Nmax], Dp[Nmax];
 
int Solve(const int left, const int right)
{
    Dp[left] = 0;
    Dp[left - 1] = 0;
 
    for (int i = left + 1; i < right; i++)
        Dp[i] = max(Dp[i - 1], Dp[i - 3] + Values[i] + Values[i - 1]);
 
    return Dp[right - 1];
}
 
int main()
{
    freopen("oo.in", "r", stdin);
    freopen("oo.out", "w", stdout);
 
    int N;
    scanf("%d", &N);
 
    for (int i = 1; i <= N; i++)
        scanf("%d", &Values[i]);
 
    if (N == 2)
    {
        printf("%d\n", Values[1] + Values[2]);
        return 0;
    }
 
    Values[N + 1] = Values[1];
    Values[N + 2] = Values[2];
 
    printf("%d\n", max(Solve(3, N + 2), max(Solve(2, N + 1), Solve(1, N))));
}