func_code: def count_letters(s):
      total = 0
      if s == '':
          return total
      else:
          i = 0
          for c in s:
              if c.isalpha():
                  t = s[:i]
                  t += '1'
                  t += s[i:]
                  s = t
              i += 1
          if not s.isupper():
              total = 0
              for c in s:
                  total += int(c)
              return total
          else:
              return count_letters(s)