N = int(input())

lst = []
m = 0
temp = [[0]]

while temp:
    p = temp.pop()
    if len(p)==N:
        lst.append(p)
    else:
        for i in range(p[-1]+2):
            s = p[:]
            s.append(i)
            temp.append(s)

lst.sort()
abc = 'abcdefghij'
for l in lst:
    print(*[abc[i] for i in l], sep='')
