{"raw_statement":[{"iden":"problem statement","content":"Iroha has a sequence of $N$ strings $S_1, S_2, ..., S_N$. The length of each string is $L$.\nShe will concatenate all of the strings in some order, to produce a long string.\nAmong all strings that she can produce in this way, find the lexicographically smallest one.\nHere, a string $s=s_1s_2s_3$...$s_n$ is _lexicographically smaller_ than another string $t=t_1t_2t_3$...$t_m$ if and only if one of the following holds:\n\n*   There exists an index $i(1≦i≦min(n,m))$, such that $s_j = t_j$ for all indices $j(1≦j<i)$, and $s_i<t_i$.\n*   $s_i = t_i$ for all integers $i(1≦i≦min(n,m))$, and $n<m$."},{"iden":"constraints","content":"*   $1 ≦ N, L ≦ 100$\n*   For each $i$, the length of $S_i$ equals $L$.\n*   For each $i$, $S_i$ consists of lowercase letters."},{"iden":"input","content":"The input is given from Standard Input in the following format:\n\n$N$ $L$\n$S_1$\n$S_2$\n:\n$S_N$"},{"iden":"sample input 1","content":"3 3\ndxx\naxx\ncxx"},{"iden":"sample output 1","content":"axxcxxdxx\n\nThe following order should be used: `axx`, `cxx`, `dxx`."}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}