{"raw_statement":[{"iden":"problem statement","content":"Iroha has a sequence of $N$ strings $s_1, s_2, ..., s_N$.\nShe will choose some (possibly all) strings from the sequence, then concatenate those strings retaining the relative order, to produce a long string.\nAmong all strings of length $K$ that she can produce in this way, find the lexicographically smallest one."},{"iden":"constraints","content":"*   $1 ≦ N ≦ 2000$\n*   $1 ≦ K ≦ 10^4$\n*   For each $i$, $1 ≦ |s_i| ≦ K$.\n*   $|s_1| + |s_2| + ... + |s_N| ≦ 10^6$\n*   For each $i$, $s_i$ consists of lowercase letters.\n*   There exists at least one string of length $K$ that Iroha can produce."},{"iden":"input","content":"The input is given from Standard Input in the following format:\n\n$N$ $K$\n$s_1$\n$s_2$\n:\n$s_N$"},{"iden":"sample input 1","content":"3 7\nat\ncoder\ncodar"},{"iden":"sample output 1","content":"atcodar\n\n`at` and `codar` should be chosen."},{"iden":"sample input 2","content":"3 7\ncoder\ncodar\nat"},{"iden":"sample output 2","content":"codarat\n\n`codar` and `at` should be chosen."},{"iden":"sample input 3","content":"4 13\nkyuri\nnamida\nzzzzzzz\naaaaaa"},{"iden":"sample output 3","content":"namidazzzzzzz\n\n`namida` and `zzzzzzz` should be chosen."}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}