#include <iostream>

using namespace std;
using LL = long long;
using ULL = unsigned long long;

int dp[1001][2];
int V[1001];

int main() {
    int N;
    cin >> N;

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

    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(dp[N][0], dp[N][1]) << endl;
}