N = int(input())

char = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j']

def search(arr):
  global N, char
  if len(arr) == N:
    ans = ''.join([char[x] for x in arr])
    print(ans)
    return
  else:
    for i in range(arr[-1] + 2):
      arr_next = arr + [i]
      search(arr_next)

search([0])