#include <fstream>

using namespace std;

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

const int DM = 1e5 + 10;

int n, p[DM], dp[DM];
int rez;
int stop[] = {0, -1, 0, 1};

void redp()
{
    for(int i = 0; i <= n + 5; i++) dp[i] = 0;
}

int main()
{
    fin >> n;
    for(int i = 1; i <= n; i++) fin >> p[i];
    p[n + 1] = p[1];

    for(int j = 1; j <= 3; j++) 
    {
        for(int i = j; i <= n + stop[j]; i++) 
            if(i - 1 >= j) dp[i] = max(dp[i - 1], p[i] + p[i - 1] + dp[i - 3]);
        rez = max(dp[n + stop[j]], rez);
        redp();
    }

    fout << rez;
    

    
}