#include <fstream>

using namespace std;

const int Nmax = 100005;

int v[Nmax];
long long dp[Nmax];

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

    int n;
    long long sol;

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

    ///Cazul 1: Luam perechea 1, 2
    dp[0] = 0;
    dp[1] = 0;
    dp[2] = v[1] + v[2];
    for(int i = 3; i <= n; i++){
        dp[i] = max(dp[i - 1], v[i] + v[i - 1] +  dp[i - 3]);
    }
    sol = dp[n - 1];

    ///Cazul 2: Luam perechea 2, 3
    dp[0] = 0;
    dp[1] = 0;
    dp[2] = 0;
    dp[3] = v[2] + v[3];
    for(int i = 4; i <= n; i++){
        dp[i] = max(dp[i - 1], v[i] + v[i - 1] +  dp[i - 3]);
    }
    sol = max(sol, dp[n]);

    ///Cazul 3: Luam perechea n, 1
    dp[0] = 0;
    dp[1] = v[1] + v[n];
    dp[2] = 0;
    for(int i = 3; i <= n; i++){
        dp[i] = max(dp[i - 1], v[i] + v[i - 1] +  dp[i - 3]);
    }
    sol = max(sol, dp[n - 2]);

    fout << sol;

    return 0;
}