#include <fstream>
using namespace std;

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

int i,T,N,K,P,v[100005],dp[100005];
int main()
{
    f>>N;
    for(i=1;i<=N;++i)
        f>>v[i];
    v[N+1]=v[1];

    for(i=1;i<=N;++i)
        dp[i]=v[i]+v[i+1];
    for (i=1;i<=N;++i)
        dp[i]=max(dp[i-2],dp[i-3]+dp[i]);
    g<<dp[N];

    return 0;
}