#!/usr/bin/perl
use strict;
use warnings;

my @x = map {$_->[0]}
	   sort {$b->[2] <=> $a->[2] ||
	         $a->[1] <=> $b->[1] }
	    map {[$_, split]} grep {/\S/} <DATA>;

for my $i (0 .. $#x) {
	print $x[$i];
	print "\n" if ($i + 1) % 3 == 0;
}
__DATA__
1.000	64.103	2840.0
1.000	42.735	2840.0
1.000	32.051	2840.0

1.050	64.103	3280.0
1.050	42.735	3280.0
1.050	32.051	3280.0

1.100	64.103	3720.0
1.100	42.735	3720.0
1.100	32.051	3720.0