#include <bits/stdc++.h>

using namespace std;
ifstream fin("oo.in");
ofstream fout("oo.out");
int n, a[100005], dp[100005];
void Citire()
{
    fin >> n;
    for(int i = 1; i <= n; i++)
        fin >> a[i];
}

void Rez()
{
    int sol = 0;
    dp[1] = a[n] + a[1];
    dp[2] = dp[1];
    for(int i = 3; i < n - 1; i++)
        dp[i] = max(dp[i - 2] + a[i] + a[i + 1], dp[i - 1]);
    sol = dp[n - 1];

    dp[1] = 0;
    dp[2] = a[1] + a[2];
    dp[3] = dp[2];
    for(int i = 4; i <= n; i++)
        dp[i] = max(dp[i - 3] + a[i] + a[i + 1], dp[i - 2]);

    sol = max(sol, dp[n]);
    fout << sol << "\n";
}
int main()
{
    Citire();
    Rez();
    return 0;
}