#include <bits/stdc++.h>

using namespace std;

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

const int N = 1e5 + 5;
int n, ans;
int v[N], dp[N];

void cleardp(){
    for(int i = 0; i <= N; i++)
        dp[i] = 0;
}

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

    dp[1] = v[1] + v[n];
    dp[2] = dp[1];
    for(int i = 3; i <= n - 2; i++){
        dp[i] = max(dp[i - 1], v[i] + v[i - 1] + dp[i - 3]);
    }
    ans = max(ans, dp[n - 2]);

    cleardp();

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

    cleardp();

    dp[3] = v[2] + v[3];
    dp[4] = dp[3];
    for(int i = 5; i <= n; i++)
        dp[i] = max(dp[i - 1], v[i] + v[i - 1] + dp[i - 3]);
    ans = max(ans, dp[n]);

    out << ans;
    return 0;
}