program Ooo;
type
tabel=array [0..100007] of longint;
var
t,v:tabel;
n,m,i,j,max1:longint;
f1,f2:text;
function max(a,b:longint):longint;
begin
if a>b then max:=a else
max:=b;
end;
begin
assign (f1,'oo.in');
assign (f2,'oo.out');
reset (f1);
rewrite (f2);
readln (f1,n);
max1:=0;
for i:=1 to n do read (f1,v[i]);
v[n+1]:=v[1];
for i:=1 to 4 do
begin
t[i]:=0;
t[i+1]:=v[i]+v[i+1];
for j:=i+2 to n-2+i do
t[j]:=max(t[j-1],t[j-3]+v[j-1]+v[j]);
if t[n-2+i]>max1 then max1:=t[n-2+i];
end;
writeln (f2,max1);
close (f1);
close (f2);
end.