#include <iostream>
#include <fstream>
using namespace std;

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

#define nmax 100005
int n, v[nmax], p[nmax], dp[nmax];

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

    // p[i] = value of pair starting at sector i
    for (int i = 1; i <= n; i++)
        p[i] = v[i] + v[i % n + 1];

    // Case 1: pairs p[1..n-1]
    dp[0] = 0; dp[1] = max(0, p[1]); dp[2] = max(dp[1], p[2]);
    for (int i = 3; i <= n - 1; i++)
        dp[i] = max(dp[i - 1], dp[i - 3] + p[i]);
    int ans = dp[n - 1];

    // Case 2: pairs p[2..n]
    dp[1] = 0; dp[2] = max(0, p[2]); dp[3] = max(dp[2], p[3]);
    for (int i = 4; i <= n; i++)
        dp[i] = max(dp[i - 1], dp[i - 3] + p[i]);
    ans = max(ans, dp[n]);

    fout << ans;
    return 0;
}