#include <bits/stdc++.h>

#define show(x) cout << #x << " = " << x << endl

using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << "sz=" << v.size() << "\n[";
    for (const auto& p : v) {
        os << p << ",";
    }
    os << "]\n";
    return os;
}

template <typename S, typename T>
ostream& operator<<(ostream& os, const pair<S, T>& p)
{
    os << "(" << p.first << "," << p.second
       << ")";
    return os;
}


constexpr ll MOD = 1e9 + 7;

template <typename T>
constexpr T INF = numeric_limits<T>::max() / 100;

int main()
{
    int N;
    cin >> N;
    vector<ll> value(N);
    for (ll i = 0; i < N; i++) {
        cin >> value[i];
    }
    vector<ll> dp[2] = {vector<ll>(N + 1, 0), vector<ll>(N + 1, 0)};  //Nコメまで最後の皿取ったか
    for (int i = 1; i <= N; i++) {
        dp[0][i] = max(dp[0][i - 1], dp[1][i - 1]);
        dp[1][i] = dp[0][i - 1] + value[i - 1];
    }
    cout << max(dp[0][N], dp[1][N]) << endl;

    return 0;
}