#include <stdio.h>
#include <algorithm>
#include <math.h>
using namespace std;
 
int dp[100005][3];
int a[100005];
 
int main()
{
    int i,n;
    freopen("oo.in", "r", stdin);
    freopen("oo.out", "w", stdout);
    scanf("%d",&n);
    for(i = 1;i <= n;i++){
        scanf("%d",&a[i]);
    }
    a[0] = a[n];
    int mx2,mx;
    mx = 0;
    mx2 = 0;
    dp[2][0] = a[1]+a[2];
    dp[3][0] = dp[2][0];
    for(i = 4;i < n;i++){
        mx = max(mx, dp[i-3][0]);
        dp[i][0] = a[i]+a[i-1]+mx;
        mx2 = max(mx2, dp[i][0]);
    }
    mx = 0;
    dp[3][1] = a[2]+a[3];
    dp[4][1] = dp[3][1];
    for(i = 5;i <= n;i++){
        mx = max(mx, dp[i-3][1]);
        dp[i][1] = a[i]+a[i-1]+mx;
        mx2 = max(mx2, dp[i][1]);
    }
    mx = 0;
    dp[1][2] = a[0]+a[1];
    dp[2][2] = dp[1][2];
    for(i = 3;i < n-1;i++){
        mx = max(mx, dp[i-3][2]);
        dp[i][2] = a[i]+a[i-1]+mx;
        mx2 = max(mx2, dp[i][2]);
    }
    printf("%d",mx2);
    return 0;
}