sub workbook {
    my ($n, $k, $arr) = @_;

    my @tmp;
    my $cnt = 0;
    my $j = 0;
    for (my $i = 0; $i < scalar(@$arr); $i++) {
        if ($arr->[$i] > $k) {
            for ($j = 1; $j <= $arr->[$i] - ($arr->[$i] % $k); $j += $k) {
                push(@tmp, [ $j..$j + $k - 1]);
            }
            push(@tmp, [$j..$arr->[$i]]) if ($arr->[$i] % $k != 0);
        } else { push(@tmp, [1..$arr->[$i]]); }
        
    }
    for (my $i = 0; $i <scalar(@tmp); $i++) {
        $cnt += grep { $_ == $i + 1} @{$tmp[$i]};
    }
    
    return $cnt;
}