#include <bits/stdc++.h>
using namespace std;

int main()
{
    cin.tie(0)->sync_with_stdio(0);

    int N;
    cin >> N;
    int V[1006];
    for (int i = 1; i <= N; i++) {
        cin >> V[i];
    }

    int dp[1006][2] = {};

    for (int i = 1; i <= N; i++) {
        dp[i][0] = max(dp[i - 1][0], dp[i - 1][1]);
        dp[i][1] = dp[i - 1][0] + V[i];
    }

    cout << *max_element(dp[N], dp[N] + 2) << endl;

    return 0;
}