use Socket;

my $str = "";

while(<>) {
  chomp;
  my ($ip,$bits) = m,^(\d+(?:\.\d+){3})/(\d+)$, or next;
  $str .= ";" . unpack("B*",inet_aton($ip));
  substr($str,-$bits) = "#" x $bits if $bits = 32 - $bits;
}
$str .= ";";
1 while $str =~ s/;([01]+)0(#*);\1.\2;/;${1}#${2};/g;

my @blocks = $str =~ /[10#]+/g;

foreach my $block (@blocks) {
  my $bits = 32 - ($block =~ tr/#/0/);
  print inet_ntoa(pack("B*", $block)),"/$bits\n";
}