In this problem, we only consider strings consisting of lowercase English letters.  Strings s and t are said to be **isomorphic** when the following conditions are satisfied:    * |s| = |t| holds.   * For every pair i, j, one of the following holds:     * s_i = s_j and t_i = t_j.     * s_i \neq s_j and t_i \neq t_j.  For example, `abcac` and `zyxzx` are isomorphic, while `abcac` and `ppppp` are not.  A string s is said to be in **normal form** when the following condition is satisfied:    * For every string t that is isomorphic to s, s \leq t holds. Here \leq denotes lexicographic comparison.  For example, `abcac` is in normal form, but `zyxzx` is not since it is isomorphic to `abcac`, which is lexicographically smaller than `zyxzx`.  You are given an integer N. Print all strings of length N that are in normal form, in lexicographically ascending order.
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))
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
ans.sort()
for i in ans:
    print(i)