use List::Util qw/sum/;

while( <INPUT> )
{
  next if /^$/;
  my ($first, $last, @grades) = split;

  my $name_index = "$last,$first";
  my $avg_grade = sum(@grades) / scalar(@grades);

  $students{$name_index}{grades}    = \@grades;
  $students{$name_index}{avg_grade} = $avg_grade;

  push @averages, $avg_grade;
}

##</code><code>##

my $i = sprintf("%d", scalar(@averages) / 2 );

##</code><code>##

my $i = int( scalar(@averages)/2 );