my %sums;
my $sum_of_pairs = 0;
 
for ($i = 1; $i < 10000; $i++) {
  $sums{$i} = d($i);
}
 
for my $k ( keys %sums ) {
    if (exists($sums{$sums{$k}}) && $k != $sums{$k} && $k == $sums{$sums{$k}}) {
        $sum_of_pairs += $k;
    }
}
 
print $sum_of_pairs . "\n";
exit;
 
sub d {
    my ($n) = @_;
    my $sum =0;
 
    for (1 .. sqrt($n)) {
        unless ($n % $_) {
            $sum += $_;
            unless ($_ == 1 || $_ == sqrt($n)) {
                $sum += ($n / $_);
            }
        }
    }
 
    return $sum;
}