N = gets.to_i
a = gets.split.map(&:to_i)
OP = [:+, :-, :*, :/]
ans = a[1..-1].inject([a[0], a[0]]) {|memo, x|
  d = memo.product(OP).map {|v, o|
    if not (x == 0 and o == :/)
      v.send(o, x)
    else
      0
    end
  }
  [d.min, d.max]
}.max
puts ans