#include<bits/stdc++.h>

using namespace std;
const int nmax=1e5+5;

int v[nmax];

inline int max(int a,int b){
    if (a>b)
        return a;
    return b;
}

inline int xx(int s,int f){
    int dp[nmax];
    memset(dp,0,sizeof(dp));
    int i;
    dp[s+1]=v[s]+v[s+1];
    for(i=s+2;i<=f;++i)
        dp[i]=max(dp[i-1],dp[i-3]+v[i]+v[i-1]);
    return dp[f];
}


int main()
{
    int sol,n,i;
    freopen("oo.in","r",stdin);
    freopen("oo.out","w",stdout);
    scanf("%d", &n);
    for (i=1;i<=n;++i)
        scanf("%d",&v[i]);
    v[0]=v[n];
    v[n+1]=v[1];
    sol=0;
    sol=max(xx(1,n-1),max(xx(2,n),xx(3,n+1)));
    printf("%d", sol);
}