sub k{
  my $s = shift;
  my @g;
  for( sort{ $$s{$b} <=> $$s{$a} || $a cmp $b } keys %$s ){
    last if $$s{$_} < 3;
    next unless $_ =~ y/a-z// > 2;
    my @f;
    push @f, ( pos($t)-3 ) while $t =~ /$_/g;
    my $g = c(n(@f));
    $g > 2 && push @g, $g
  }
  return c(@g)
}