#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)

int main()
{
	cin.tie(0);
	ios::sync_with_stdio(false);

	int N; cin >> N;

	int dp[1010][2];
	rep(i, 0, 1010) rep(j, 0, 2) dp[i][j] = 0;

	rep(i, 0, N)
	{
		int V; cin >> V;
		dp[i + 1][0] = max(dp[i][0], dp[i][1]);
		dp[i + 1][1] = dp[i][0] + V;
	}

	cout << max(dp[N][0], dp[N][1]) << endl;
}