#include <iostream>
#include <algorithm>

using namespace std;


int main() {
	int dp[2][1005];
	int v[1005];
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> v[i];
	}
	dp[0][1] = 0;
	dp[1][1] = v[1];
	for (int i = 2; i <= n; i++) {
		dp[0][i] = max(dp[0][i - 1], dp[1][i - 1]);
		dp[1][i] = dp[0][i - 1] + v[i];
	}
	cout << max(dp[0][n], dp[1][n]) << endl;
	return 0;
}