#include <bits/stdc++.h>

using namespace std;

const int N = 1e3 + 5;

int n, a[N], f[N][2];

int main()
{
	cin >> n;
	for (int i = 1; i <= n; i ++ ) cin >> a[i];
	for (int i = 1; i <= n; i ++ ) f[i][0] = max(f[i - 1][0], f[i - 1][1]), f[i][1] = f[i - 1][0] + a[i];
	cout << max(f[n][0], f[n][1]);
	return 0;
}