#include <iostream>
#include <cmath>
#include <string>
#include <vector>
#include <map>
#include <list>
#include <deque>
#include <algorithm>

using namespace std;

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

	vector<int>susiV(n);
	for (int i = 0; i < n; i++) {
		cin >> susiV[i];
	}

	vector<int>dp(2);
	for (int i = 0; i < n; i++) {
		vector<int> dptmp(2);
		dptmp[0] = max(dp[0], dp[1]);
		dptmp[1] = dp[0] + susiV[i];
		dp = dptmp;
	}

	int ans = max(dp[0], dp[1]);
	cout << ans << endl;
	return 0;
}