#include <iostream>

using namespace std;

int solve(int n, int v[]) {
    int dp[n+1];
    dp[0] = 0; dp[1] = v[0];

    bool flag = true;
    for (int i = 1; i < n; i++) {
        if (flag) {
            if (dp[i] < dp[i-1]+v[i]) {
                dp[i+1] = dp[i-1] + v[i];
                flag = true;
            } else {
                dp[i+1] = dp[i];
                flag = false;
            }
        } else {
            dp[i+1] = dp[i] + v[i];
            flag = true;
        }
    }
    return dp[n];
}

int main(int argc, char const* argv[]) {
    int n; cin >> n;
    int v[n]; for (int i = 0; i < n; i++) {cin >> v[i];}
    cout << solve(n, v) << endl;
    return 0;
}