ComputerCraft Computer Formatter

while true do
term.clear()
term.setCursorPos(1,1)
print("WARNING: You are attempting to format this computer! This process is irreverible!")
print("Do you wish to continue? Yes/No")
local input = read()

if input == "Yes" or input == "yes" or input == "YES" then
shell.run("label","clear")
for _,file in ipairs(fs.list("/")) do
  if not fs.isReadOnly(file) then
    fs.delete(file)
  end
end
print("Format Complete")
  sleep(2)
  os.reboot()
elseif input == "No" or input == "no" or input == "NO" then
    print("Terminating Program")
    break
else
    print("Invalid Input! Try again")
    sleep(3)
end
end