#include <bits/stdc++.h>
#ifdef __LOCAL
    #define DBG(X) cout << #X << " = " << (X) << endl;
    #define SAY(X) cout << (X) << endl;
    #include <filesystem>
    namespace fs = std::filesystem;
#else
    #define DBG(X)
    #define SAY(X)
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[]={1, 0, -1, 0, 1,-1, 1,-1};
int dy[]={0, 1, 0, -1, 1, 1,-1,-1};
const int INT_INF = (int)(2e9);
const ll  LL_INF = (ll)(2e18);
static mt19937 _g(time(nullptr));
 
inline ll randint(ll a, ll b) { ll w = (_g() << 31LL) ^ _g(); return a + w % (b - a + 1); }
inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p << "]"; return os; }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const map<T, S> p) { for (auto el : p) cout << "[" << el.first << ";" << el << "]"; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for (auto el : v) cout << el << " "; return os; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for (auto& elem : ret) cin >> elem; return ret; }

int N;
vector<ll> A;
void input(){
    fast_io();
    #ifdef __LOCAL
        fs::path __p = __FILE__;
        fs::path __input, __output;
        __input = __output = __p.parent_path();
        __input += string("/input/") + string(__p.stem()) + string(".txt");
        __output += string("/output/") + string(__p.stem()) + string(".txt");
        freopen(__input.c_str(), "r", stdin);
        freopen(__output.c_str(), "w", stdout);
    #endif
    cin >> N;
    A = fetch_vec<ll>(N);
}

int solve(){
    map<int,ll> dp[20010][2];
    // memset(dp,0,sizeof(dp));
    dp[0][0][0] = 0;
    dp[0][1][1] = A[0];
    for (int i = 1; i < N; i++)
    {
        for (int j = i/2-1; j <= (i+1)/2 && j<=N/2; j++)
        {
            dp[i][0][j] = max(dp[i-1][0][j],dp[i-1][1][j]);
            dp[i][1][j] = dp[i-1][0][j-1]+A[i];
        }
        
    }
    ll ans;
    ans = max(dp[N-1][0][N/2],dp[N-1][1][N/2]);
    DBG(ans)
    cout << ans << endl;
    
    return 0;
}   

int main()
{
    input();
    solve();
    return 0;
}
