def solve(li):
    if len(li) == n:
        ans.append(li)
        return
    for i in range(1, li[-1] + 2):
        solve(li + [i])

ans = []
n = int(input())
solve([1])
res = []
alph = "abcdefghijklmnopq"

for ptn in ans:
    for i in range(n):
        ptn[i] = alph[ptn[i] - 1]
    res.append("".join(ptn))
res = sorted(res)
for i in res:
    print(i)
    