var a: array[1..5]of byte;
    s,t,i,n,max: integer;
begin
readln(n);
for i:=1 to 5 do
begin
  readln(a[i]);
  s:=s+a[i]
end;
max:=s;
for i:=6 to n do
begin
  readln(t);
  s:=s-a[i-5]+t;
  if s > max then
    max:=s
end;
writeln(max);
end.