#include <fstream>
using namespace std;
ifstream f("oo.in");
ofstream g("oo.out");
int n,i,S,v[1<<17],dp[1<<17];
void rez(int s,int e)
{
    dp[s]=0;
    dp[s+1]=v[s]+v[s+1];
    for(i=s+2;i<=e;++i)
        dp[i]=max(dp[i-1],dp[i-3]+v[i-1]+v[i]);
    S=max(S,dp[e]);
}
int main()
{
    f>>n;
    for(i=1;i<=n;++i) f>>v[i];
    v[n+1]=v[1];
    rez(1,n-1);
    rez(2,n);
    rez(3,n+1);
    g<<S;
    return 0;
}