local function chsize(char)
    if not char then
        return 0
    elseif char > 240 then
        return 4
    elseif char > 225 then
        return 3
    elseif char > 192 then
        return 2
    else
        return 1
    end
end
 
function utf8sub(str, startChar, numChars)
  local startIndex = 1
  while startChar > 1 do
      local char = string.byte(str, startIndex)
      startIndex = startIndex + chsize(char)
      startChar = startChar - 1
  end
 
  local currentIndex = startIndex
 
  while numChars > 0 and currentIndex <= #str do
    local char = string.byte(str, currentIndex)
    currentIndex = currentIndex + chsize(char)
    numChars = numChars -1
  end
  return str:sub(startIndex, currentIndex - 1)
end