loop do
  n, k = STDIN.gets.chomp.split(' ').map(&:to_i)
  if n == 0 && k == 0 then break end
  
  cs = (1..n.to_i).map{
    STDIN.gets
  }.map(&:chomp).map(&:to_i)
  
  cd = (0..(cs.length - k)).map{|m| cs[m..(m + k - 1)].inject(:*)}.max
  
  ck = cs.sort.reverse[0..k-1].inject(:*)
  
  puts ck - cd < 0 ? "NO GAME" : (ck == cd ? 0 : ck - cd)
end