#include <iostream>
#include <sstream>
#include <vector>
#include <algorithm>
#include <string>
#include <functional>
#include <numeric>
#include <ctype.h>
#include <cstdlib>
#include <string.h>
#include <cmath>
#include <cstdio>
#include <map>
#include <queue>
#include <utility>

using namespace std;

const int INF = 1000000007;
const double PI = acos(-1.0);

int dp[1002];
vector<int> vec;
int main()
{
	int N, input;
	cin >> N;
	for (int i = 0; i < N; i++)
	{
		cin >> input;
		vec.push_back(input);
	}

	for (int i = N - 1; i >= 0; i--)
		dp[i] = max(dp[i + 1], dp[i + 2] + vec[i]);
	
	cout << dp[0] << endl;

}