var
  n,i,max:longint;
  a,s:array[0..100000]of longint;

function min(x,y:longint):longint;
begin
  if x<y then exit(x);
  exit(y);
end;

procedure go(k,last,money,who:longint);
var
  i:longint;
begin
  if k>n then
  begin
    if money>max then max:=money;
    exit;
  end;

    for i:=1 to min(last*2,n-k+1) do
    begin
      if who=1 then go(k+i,i,money+s[k+i-1]-s[k-1],who xor 1)
      else go(k+i,i,money,who xor 1);
    end;
end;

begin
  assign(input,'xoinc.in'); reset(input);
  assign(output,'xoinc.out'); rewrite(output);
  readln(n);
  for i:=1 to n do
  begin
    read(a[i]);
    s[i]:=s[i-1]+a[i];
  end;
  max:=-maxlongint;
  go(1,1,0,1);
  writeln(max);
  close(input);
  close(output);
end.