#include <bits/stdc++.h>
#define NMAX 200001
#define MAX 1001
//#define int long long
#define pb push_back
#define eb emplace_back
#define MOD 1000000007
#define nl '\n'
#define INF 10000000007
#define LLONG_MAX 9223372036854775807
#define pii pair<int,int>
#define tpl tuple<int,int,int>
#pragma GCC optimize("O3")
using namespace std;
ifstream fin("oo.in");
ofstream fout("oo.out");
int n,v[NMAX],dp[NMAX];
bool used[NMAX];
signed main() {

    fin>>n;
    for(int i=1;i<=n;++i)
    {
        fin>>v[i];
        v[i+n]=v[i];
    }
    for(int i=1;i<=n;++i)
    {
        dp[i]=v[i]+v[i+1];
        for(int j=i+3;j<i+n;++j)
        {
            dp[i]+=(v[j]+v[j+1]);
            j+=3;
        }
    }
    int maxi=0;
    for(int i=1;i<=n;++i)
    {
        maxi=max(dp[i],maxi);
    }
    fout<<maxi;

    return 0;
}