#include <cstdio>
#include <algorithm>

#define NMax 100005

using namespace std;

int N, S, X[NMax], DP[NMax];

void Read ()
{
    freopen ("oo.in", "r", stdin);
    scanf ("%d", &N);
    for (int i=1; i<=N; ++i)
    {
        scanf ("%d", &X[i]);
    }
    X[N+1]=X[1];
}

void Print ()
{
    freopen ("oo.out", "w", stdout);
    printf ("%d\n", S);
}

void Solve (int L, int R)
{
    DP[L-2]=0;
    DP[L-1]=X[L-1]+X[L-2];
    for (int i=L; i<=R; ++i)
    {
        DP[i]=max (DP[i-1], DP[i-3]+X[i]+X[i-1]);

    }
            S=max (S, DP[R]);
}

int main()
{
    Read ();
    Solve (3, N-1);
    Solve (4, N);
    Solve (5, N+1);
    Print ();
    return 0;
}