#include<bits/stdc++.h>
#define int long long
using namespace std;
int read()
{
    int x=0,w=1;
    char ch=0;
    while(ch<'0'||ch>'9')
    {
        if(ch=='-') w=-1;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9')
    {
        x=(x<<1)+(x<<3)+(ch^48);
        ch=getchar();
    }
    return x*w;
}
void write(int x)
{
    if(x<0)
    {
        x=-x;
        putchar('-');
    }
    if(x>=10) write(x/10);
    putchar((x%10)^48);
}
int n,a[1000005];
int dist(int i,int j){return min(abs(i-j),n-abs(i-j));}
signed main()
{
    freopen("transportt.in","r",stdin);
    freopen("transportt.out","w",stdout);
    n=read();
    int ans=0;
    for(int i=1;i<=n;i++) a[i]=read();
    for(int i=1;i<=n;i++)
    {
        for(int j=i+1;j<=n;j++) ans=max(ans,a[i]+a[j]+dist(i,j));
    }
    write(ans);
    fclose(stdin);
    fclose(stdout);
    return 0;
}