def calcs(x,y,ax,ay,bx,by) ((ax-x)*(by-y)-(bx-x)*(ay-y))/2.0 end
def inpf() a=gets.chomp.split(" ").map(&:to_f)end
def inps() a=gets.chomp.split(" ")end  
def copy(a) Marshal.load(Marshal.dump(a)) end
def kaizyo(n)(n < 2)? 1 : (2..n).inject(:*) end
def scount(a) b=na(a.max+1);a.each{|n|b[n]+=1};return b end
def na(n=0,d=0) Array.new(n,d)end
def na2(n=0,m=0,d=0) Array.new(n){Array.new(m,d)}end
def na3(n=0,m=0,l=0,d=0) Array.new(n){Array.new(m){Array.new(l,d)}}end
def bit(n) n.to_s(2).split("").map(&:to_i) end
def inp() a=gets.chomp.split(" ").map(&:to_i)end
def ser(a,x,s)
  if(x >= a.size)
    @ans = [@ans,s].max
    return
  end
  ser(a,x+1,s*a[x])
  if((s > 0 and a[x] > 0) or (s < 0 and a[x] < 0))
    ser(a,x+1,s+a[x]) 
  else
    ser(a,x+1,s-a[x])
  end
end
@n = inp[0]
t = inp
@ans = -99999999
ser(t,1,t[0])
#ser2(t,1,t[0])
p @ans
=begin
=end