my (@candidate, %freq);
while (<DATA>) {
    chomp;
    my @list = split ' ';
    push @candidate, \@list;
    for my $word (@list) {
        ++$freq{$_} for split //, $word;
    }
}
my $tot = sum(values %freq);
$freq{$_} = ($freq{$_} / $tot) * 100 for keys %freq;

my (@solution, %let);
for my $list (@candidate) {
    my ($best, $item) = (0, '');
    for my $word (@$list) {
        my $score = sum(map $freq{$_}, split //, $word);
        ($best, $item) = ($score, $word) if $score > $best;
    }
    ++$let{$_} for split //, $item;
    push @solution, $item;
}
my $total = sum(map {my $n = $let{$_}; ($n * $n + $n) / 2} keys %let);
print "$total : [ @solution ]\n";