<?php
    //一行分を読み込む, 空白で分割してそれぞれ$aと$bの変数に入れる
    $arryList = explode(" ", trim(fgets(STDIN)));
    for ($i = 0; $i < count($arryList); $i++) {
         $narabi[] = $arryList[$i];
         for ($j = 0; $j < count($narabi); $j++) {
              if ($narabi[$j] > $narabi[$i]) {
                  $tmp = $narabi[$j];
                  $narabi[$j] = $narabi[$i];
                  $narabi[$i] = $tmp;
              }
         }
    }
    
    foreach ($narabi as $value) {
        echo $value;
    }