use strict;
use warnings;
my %hash;
while (my $line=<STDIN>){
  foreach my $word (  split( /[^a-zA-Z]+/ , $line)   ){
    my $len = length($word);
    $hash{lc $word}++ if 2<=$len && $len < 5;
  }
}
print $_."\n" for sort keys %hash;