import collections, itertools

def isFromBananania(t):
   c = collections.defaultdict(int)
   for x in t:
      c[x] += 1
      if c['b'] > c['a']:
         return False
   if c['b'] == c['a']:
      return True
   else:
      return False

def generateBanananiaElection(n):
   l = itertools.product('ab', repeat=n)
   for t in l:
      if isFromBananania(t):
         print ''.join(t)

if __name__ == "__main__":
   for i in [x+1 for x in range(5)]:
      print i*2
      generateBanananiaElection(i*2)