enum_a = File.open(ARGV.shift).each
enum_b = File.open(ARGV.shift).each

interleaved = Enumerator.new do |yielder|
  line_a = enum_a.next
  line_b = enum_b.next
  
  while line_a or line_b
    yielder.yield line_a if line_a
    yielder.yield line_b if line_b
    
    line_a = enum_a.next
    line_b = enum_b.next
  end
end

puts interleaved.count