N = int(input())
ans = ['a']
moji = ['a','b','c','d','e','f','g','h','i','j']
count = 1
while count < N:
    tmp = []
    for i in ans:
        for k in range(len(set(list(i)))+1):
            tmp.append(i+moji[k])
    count += 1
    ans = tmp
print(sorted(ans))