#include <iostream>

using namespace std;

const int MAXN = 1000;

int N;
int V[MAXN];
int dp[MAXN][2];

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