The input number of one function

[mauro3]

I think you should

function a(files, images)
  for i=1:2:length(files)
    ...
  end
end

if you really want to pass them in a separate arguments

function a(args...)
  files = args[1:2:end÷2]
  imgs = args[2:2:end÷2]
  for i=1:length(files)
    ..
  end
end