sub func { $_[0] ** 2 * $_[1] }
sub group_hero_blunt {
    use bigint;
    
    my @nums = sort { $a <=> $b } @_;
    
    my $sum = 0;
    for my $i ( 0 .. $#nums ) {
        for my $j ( 0 .. $i - 1 ) {
            $sum += func( $nums[ $i ], $nums[ $j ]) *
                2 ** ( $i - $j - 1 )
        }
        $sum += func( $nums[ $i ], $nums[ $i ])
    }
    return $sum
}