#include <bits/stdc++.h> 

using namespace std;
typedef long long ll;

const int MAX = 1001;
int N;
int V[MAX];
int dp[MAX][2];

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

    dp[1][0] = 0;
    dp[1][1] = V[1];

    for (int i = 2; i <= N; i++) {
        dp[i][1] = max(dp[i - 1][1], dp[i - 1][0] + V[i]);
        dp[i][0] = max(dp[i - 1][0], dp[i - 1][1]);
    }

    cout << dp[N][1] << endl;
    // for (int i = 1; i <= N; i++) {
    //     cout << dp[i][0] << " " << dp[i][1] << endl;
    // }
}