#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)s; i < (int)e; ++i)
#define all(a) (a).begin(), (a).end()

int main() {
    cin.tie(nullptr);
    
    int N;
    cin >> N;
    
    vector dp(N, vector<ll>(2));
    vector<ll> V(N);
    rep(i, 0, N) cin >> V[i];
    
    dp[0][0] = V[0];
    dp[0][1] = 0;
    
    rep(i, 1, N) {
        dp[i][0] = dp[i - 1][1] + V[i];
        dp[i][1] = max(dp[i - 1][0], dp[i - 1][1]);
    }
    
    cout << max(dp[N - 1][0], dp[N - 1][1]) << '\n';
}