#include <iostream>
#include <cstdio>
#define MAXN 100050

using namespace std;

int n, rez, a[MAXN], din[MAXN];

void solve(int st, int dr)
{
    din[st] = 0;
    din[st+1] = a[st] + a[st+1];
    for (int i = st+2; i <= dr; i++)
        din[i] = max(din[i-1], a[i-1] + a[i] + din[i-3]);
    rez = max(rez, din[dr]);
}

int main()
{
    freopen("oo.in", "r", stdin);
    freopen("oo.out", "w", stdout);

	scanf("%d", &n);
    for (int i = 1; i <= n; i++)
		scanf("%d", &a[i]);
    a[n+1] = a[1];
    solve(1, n-1);
    solve(2, n);
    solve(3, n+1);
    printf("%d", rez);

    return 0;
}