#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int, int>;

int dp[1010][2];

int main() {
    int n;
    cin >> n;
    for (int i = 0, v; i < n; i++) {
        cin >> v;
        dp[i + 1][0] = max({ dp[i + 1][0], dp[i][0], dp[i][1] });
        dp[i + 1][1] = max(dp[i + 1][1], dp[i][0] + v);
    }
    cout << max(dp[n][0], dp[n][1]) << endl;
}