{"raw_statement":[{"iden":"problem statement","content":"In this problem, we only consider strings consisting of lowercase English letters.\nStrings $s$ and $t$ are said to be **isomorphic** when the following conditions are satisfied:\n\n*   $|s| = |t|$ holds.\n*   For every pair $i, j$, one of the following holds:\n    *   $s_i = s_j$ and $t_i = t_j$.\n    *   $s_i \\neq s_j$ and $t_i \\neq t_j$.\n\nFor example, `abcac` and `zyxzx` are isomorphic, while `abcac` and `ppppp` are not.\nA string $s$ is said to be in **normal form** when the following condition is satisfied:\n\n*   For every string $t$ that is isomorphic to $s$, $s \\leq t$ holds. Here $\\leq$ denotes lexicographic comparison.\n\nFor example, `abcac` is in normal form, but `zyxzx` is not since it is isomorphic to `abcac`, which is lexicographically smaller than `zyxzx`.\nYou are given an integer $N$. Print all strings of length $N$ that are in normal form, in lexicographically ascending order."},{"iden":"constraints","content":"*   $1 \\leq N \\leq 10$\n*   All values in input are integers."},{"iden":"input","content":"Input is given from Standard Input in the following format:\n\n$N$"},{"iden":"sample input 1","content":"1"},{"iden":"sample output 1","content":"a"},{"iden":"sample input 2","content":"2"},{"iden":"sample output 2","content":"aa\nab"}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}