#include <fstream>

using namespace std;

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

int n;
int v[100002];
int dp[100002];

int din(int st, int dr)
{
    dp[st] = 0;
    dp[st+1] = v[st] + v[st+1];

    for (int i=st+2; i<=dr; i++)
        dp[i] = max(dp[i-1], dp[i-3] + v[i-1] + v[i]);

    return dp[dr];
}

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

    g << max(din(1, n-1), max(din(2, n), din(3, n+1)));

    return 0;
}