#include <fstream>
#include <iostream>
#include <vector>
#include <bitset>
#include <string.h>
#include <algorithm>
#include <iomanip>
#include <math.h>
#include <time.h>
#include <stdlib.h>
#include <set>
#include <map>
#include <string>
#include <queue>
#include <deque>

using namespace std;

const char infile[] = "oo.in";
const char outfile[] = "oo.out";

ifstream fin(infile);
ofstream fout(outfile);

const int MAXN = 100005;
const int oo = 0x3f3f3f3f;

typedef vector<int> Graph[MAXN];
typedef vector<int> :: iterator It;

const inline int min(const int &a, const int &b) { if( a > b ) return b;   return a; }
const inline int max(const int &a, const int &b) { if( a < b ) return b;   return a; }
const inline void Get_min(int &a, const int b)    { if( a > b ) a = b; }
const inline void Get_max(int &a, const int b)    { if( a < b ) a = b; }

int N, A[MAXN];
int dp[MAXN], Ans;

inline void buildDP(const int &st, const int &dr) {
    dp[st - 2] = 0;
    dp[st - 1] = A[st - 1] + A[st - 2];
    for(int i = st ; i <= dr ; ++ i)
        dp[i] = max(dp[i - 1], dp[i - 3] + A[i] + A[i - 1]);
    Ans = max(Ans, dp[dr]);
}

int main() {
    fin >> N;
    for(int i = 1 ; i <= N ; ++ i)
        fin >> A[i];
    A[N + 1] = A[1];
    for(int i = 0 ; i < 3 ; ++ i)
        buildDP(i + 3, N - 1 + i);
    fout << Ans << "\n";
    fin.close();
    fout.close();
    return 0;
}