// {{{ Templates
#include <bits/stdc++.h>

#define show(x) cerr << #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 = (ll)1e9 + 7LL;

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

// }}}

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N;
    cin >> N;
    vector<int> v(N);
    for (int i = 0; i < N; i++) {
        cin >> v[i];
    }
    vector<vector<int>> dp(N + 1, vector<int>(2, 0));  //i枚目まで取ってlastを取ったか

    for (int i = 1; i <= N; i++) {
        dp[i][1] = dp[i - 1][0] + v[i - 1];
        dp[i][0] = max(dp[i - 1][0], dp[i - 1][1]);
    }
    int maxi = max(dp[N][0], dp[N][1]);
    cout << maxi << endl;
    return 0;
}