public class UniqueCombinations {
    public static void find(String s) { find("", s); }
    private static void find(String prefix, String s) {
        if(prefix.length()==4){
        System.out.println(prefix);
        }
        for (int i = 0; i < s.length(); i++)
            find(prefix + s.charAt(i), s.substring(i + 1));

    }  
    public static void main(String[] args) {
       String st = "12345";
       find(st);
       System.out.println();
      }
}