#include <fstream>
#include <algorithm>

using namespace std;

const int NMAX= 100000;

ifstream in("oo.in");
ofstream out("oo.out");

int v[NMAX+1], d[NMAX+1];
int N, ans = 0, aux = 0;

int main(  )
{
    in >> N;
    for( int i= 1; i<=N; ++i ) {
        in >> v[i];
    }

    v[N+1] = v[1];
    for( int i = 1;  i <= 4;  ++i ) {
        aux = N - 2 + i;
        d[i] = 0;
        d[i+1] = v[i] + v[i+1];

        for( int j = i+2;  j <= aux;  ++j ) {
            d[j] = max( d[j-1], d[j-3] + v[j] + v[j-1] );
        }

        ans = max( ans, d[aux] );
    }

    out << ans << '\n';

    return 0;
}