n = int(input())
q = ["0"]
cnt = 0
while cnt < n - 1:
    qt = []
    for num in q:
        lastnum = num[-1]
        for i in range(int(lastnum) + 2):
            qt += [num + str(i)]
    q = qt.copy()
    cnt += 1
    
alp = "abcdefghijkl"
    
def show(num):
    ret = ""
    l = len(num)
    for i in range(l):
        ret += alp[int(num[i])]
    return ret

q.sort()

for num in q:
    print(show(num))