#include "bits/stdc++.h"
using namespace std;

int main() {
	int N, V[1000], DP[1010][2] = {};
	cin >> N;
	for (int i = 0; i < N; i++) cin >> V[i];
	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 - 1];
	}
	cout << max(DP[N][0], DP[N][1]) << endl;
}