#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#ifdef LOCAL
#include "algo/debug.h"
#else
#define debug(...) (void(0))
#endif
void run_case();
int main() {
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(nullptr);
	int T = 1;
	// cin >> T;
	while (T--) run_case();
	return 0;
}
void run_case() {
	int N;
	cin >> N;
	vector dp(N + 1, vector<ll>(2, 0));
	for(int i = 0; i < N; i++) {
		int V;
		cin >> V;
		dp[i + 1][1] = max(dp[i][0] + V, dp[i + 1][1]);
		dp[i + 1][0] = max(dp[i][0], dp[i][1]);
	}
	cout << max(dp[N][0], dp[N][1]) << endl;
}