Program oo;
 var a,b:array [1..100002] of longint;
     b1:array [1..1 shl 15] of char;
    i,n,rez:longint;
    fi,fo:text;
function max(a,b:longint):longint;
 begin
  if a>b then max:=a else max:=b;
 end;
procedure solve(x,y:longint);
 begin
  b[x-2]:=0; b[x-1]:=a[x-1]+a[x-2];
 for i:=x to y do begin
                    b[i]:=max(b[i-1],a[i]+a[i-1]+b[i-3]);
                    if b[i]>rez then rez:=b[i];
                    end;
end;
begin
 assign(fi,'oo.in');
  assign(fo,'oo.out');
 settextbuf(fi,b1);
 reset(fi); rewrite(fo); readln(fi,n);
 for i:=1 to n do read(fi,a[i]);
  a[n+1]:=a[1];
 solve(3,n-1); solve(4,n); solve(5,n+1);
   write(fo,rez);
  close(fo);
end.