numlist = ""

File.open("numlist.txt") do |file|
  while line = file.gets
    numlist << line
  end
end

max = 1
prod = 1
a = 0
b = 4

until b == numlist.length
  numlist[a..b].each_byte do |x|
    prod *= x.chr.to_i
  end
  if prod > max
    max = prod
  end
  prod = 1
  a += 1
  b += 1
end

puts max