sub repeated_substring {
   my ($ssl,$pos) = (1,-1);
   my $len = length($_[0]);
   my $i = 0;
   while ($i < $len-2*$ssl) {
      if (index($_[0],substr($_[0],$i,$ssl),$i+$ssl) == -1) { $i++; next }
      $pos = $i; $ssl++;
   }
   return $pos == -1 ? "" : substr($_[0], $pos, $ssl-1);
}


##</code><code>##

sub findlcs {
   my @ret;
   for my $i (0..$#_-1) {
      for my $j ($i..$#_) {
         my $str = join ":", @_[$i,$j];
         my $ans = repeated_substring($str);
         push @ret, $ans;
      }
   }
   return (sort { length($a) <=> length($b) } @ret)[0];
}