use strict;
use warnings;
use feature 'say';

my %data;

for (0..14) {
    my ($lpn, $ppn, $cnt_subppn) = get_ns();
    push @{ $data{$lpn}{$ppn} }, (0..$cnt_subppn);
}

for my $lpn ( sort {$a <=> $b} keys %data ) {
    say "$lpn:";
    for my $ppn ( sort {$a <=> $b} keys %{ $data{$lpn} } ) {
        say "  $ppn:";
        for my $sub_ppn ( sort {$a <=> $b} @{ $data{$lpn}{$ppn} } ) {
            say "    $sub_ppn";
        }
    }
}


sub get_ns {
    return (int(rand(10)), int(rand(10)), int(rand(10)));
}