#include <stdio.h>
#include <algorithm>
#include <math.h>
using namespace std;

#define ll long long unsigned
#define pb push_back
#define mp make_pair

int dp[100005][3];
int a[100005];

int main()
{
    freopen("oo.in", "r", stdin);
    freopen("oo.out", "w", stdout);
    int i,n;
    scanf("%d",&n);
    for(i = 1;i <= n;i++){
        scanf("%d",&a[i]);
    }
    a[0] = a[n];
    int mx2,mx;
    mx = 0;
    mx2 = 0;
    for(i = 1;i < n;i++){
        if(i < 3){
            dp[i][0] = dp[i-1][0]+a[i];
        }else{
            mx = max(mx, dp[i-3][0]);
            dp[i][0] = a[i]+a[i-1]+mx;
        }
        mx2 = max(mx2, dp[i][0]);
    }
    mx = 0;
    for(i = 2;i <= n;i++){
        if(i < 4){
            dp[i][1] = dp[i-1][1]+a[i];
        }else{
            mx = max(mx, dp[i-3][1]);
            dp[i][1] = a[i]+a[i-1]+mx;
        }
        mx2 = max(mx2, dp[i][1]);
    }
    mx = 0;
    for(i = 0;i < n-1;i++){
        if(i < 2){
            dp[i][2] = dp[i-1][2]+a[i];
        }else{
            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;
}