#include <bits/stdc++.h>
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][0] = dp[i][0];
		dp[i + 1][1] = dp[i][0] + v[i];
		dp[i + 1][0] = max(dp[i][1], dp[i + 1][0]);
	}
	cout << max(dp[n][0], dp[n][1]) << endl;
	return 0;
}