function get(lengh, from)
  str=""
  all = {"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g", "h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"}
  from = from or all
  for i=1, lenght do str = str..from[math.random(1, #all)] end
  return str
end