// No.45 回転寿司
#include <iostream>
#include <vector>
using namespace std;

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