#!/usr/bin/perl
#
# Convert IP to hostname (domain name)
#

while ($ln = <STDIN>){
    if ($ln =~ /^(\d+\.\d+\.\d+\.\d+)/) {
        $ip = $1; $rest = $';
        if ($host = gethostbyaddr(pack("C4", split(/\./, $ip)), 2)) {
            $ln = $host . $rest;
        }
    }
    print $ln;
}
exit;