#include<bits/stdc++.h>
using namespace std;
typedef long long int lld;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define trav(a,v) for(auto a:v)
class ST{
lld tree[4000000];
public:
void build(int a, int b, int node){
if(a==b){
tree[node]=0;
return;
}
int mid=(a+b)/2;
build(a,mid,2*node);
build(mid+1,b,2*node+1);
tree[node]=max(tree[node*2],tree[node*2+1]);
}
void update(int a, int b, int node, int pos, lld val){
if(pos<a || b<pos)return;
if(a==b){
tree[node]=val;
return;
}
int mid=(a+b)/2;
update(a,mid,2*node,pos,val);
update(mid+1,b,2*node+1,pos,val);
tree[node]=max(tree[node*2],tree[node*2+1]);
}
lld query(int a, int b, int node, int x, int y){
if(x>y)return -100000000000;
if(b<x || y<a)return -100000000000;
if(x<=a && b<=y)return tree[node];
int mid=(a+b)/2;
return max(query(a,mid,2*node,x,y),query(mid+1,b,2*node+1,x,y));
}
};
int main(){
srand(time(NULL));
int n,q;
scanf("%d",&n);
lld arr[n];
rep(i,0,n){
scanf("%lld",&arr[i]);
//arr[i]=rand()%100;
}
//scanf("%d",&q);
ST *S=new ST();
S->build(0,n-1,1);
rep(i,0,n)S->update(0,n-1,1,i,arr[i]);
set<int> candidates;
vector<int> V[n];
for(int i=n-1;i>-1;i--){
for(set<int>::iterator it=candidates.begin();it!=candidates.end();it++){
//cout<<a<<" "<<i<<" "<<S->query(0,n-1,1,i+1,a-1)<<endl;
int a=*it;
if(S->query(0,n-1,1,i+1,a-1)<min(arr[i],arr[a])){
V[i].push_back(a);
}
if(S->query(0,n-1,1,i+1,a-1)>arr[i]){
it=candidates.end();
it--;
}
}
trav(a,candidates){
//cout<<a<<" "<<i<<" "<<S->query(0,n-1,1,i+1,a-1)<<endl;
if(S->query(0,n-1,1,i+1,a-1)>=arr[a]){
candidates.erase(a);
}
}
candidates.insert(i);
}
lld ans=0;
rep(i,0,n){
trav(a,V[i]){
//cout<<a<<" ";
ans=max(ans,arr[i]+arr[a]+S->query(0,n-1,1,2*a-i,n-1));
}//cout<<endl;
}
cout<<ans<<endl;
/*lld ans2=0;
rep(i,0,n){
rep(j,i+1,n){
rep(k,2*j-i,n){
ans2=max(ans2,arr[i]+arr[j]+arr[k]);
}
}
}
rep(i,0,n){
rep(j,i+1,n){
rep(k,2*j-i,n){
if(arr[i]+arr[j]+arr[k]==ans2)cout<<i<<" "<<j<<" "<<k<<endl;
}
}
}
cout<<ans2<<endl;
if(ans!=ans2){
rep(i,0,n)cout<<arr[i]<<" ";
cout<<endl;
}*/
return 0;
}
