text: # Problem: https://docs.google.com/document/d/1nivnnq4IlPDeW0sA_d7FHa4NNKOWE8uQSGSwPXALEZw/edit?usp=sharing
  
  valid = False
  while not valid:
      # prompt the user for a word
      w = input('Enter a word: ')
      
      if len(w) in range(1, 101):
          # determine and display the distinct letters of the word
          n = len(set(w.lower()))
          print(f'The number of distinct letters appearing in W: {n}')
          
          valid = True
      else:
          print('Enter the word whose length is between 1 and 100 inclusive! \n')
  