#include <fstream>

using namespace std;

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

const int Nmax = 100005;
int v[Nmax],dp[Nmax];

int main()
{
    int N,i,nmax;
    fin >> N;
    for(i=1;i<=N;i++)
        fin >> v[i];
    for(i=5;i<N;i++)
        dp[i] = max(dp[i-3]+v[i-1]+v[i], dp[i-1]);
    nmax = dp[N-1]+v[1]+v[2];
    for(i=1;i<=N;i++)
        dp[i] = 0;
    for(i=4;i<=N-2;i++)
        dp[i] = max(dp[i-3]+v[i-1]+v[i], dp[i-1]);
    nmax = max(nmax, dp[N-2]+v[N]+v[1]);
    for(i=1;i<=N;i++)
        dp[i] = 0;
    for(i=6;i<=N;i++)
        dp[i] = max(dp[i-3]+v[i-1]+v[i], dp[i-1]);
    nmax = max(nmax, dp[N]+v[2]+v[3]);
    for(i=1;i<=N;i++)
        dp[i] = 0;
    for(i=4;i<=N;i++)
        dp[i] = max(dp[i-3]+v[i-1]+v[i], dp[i-1]);
    nmax = max(nmax, dp[N]);
    fout << nmax;
    return 0;
}