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

  my %cache = (1 => 0);
  sub _three_n_plus_1 {
    no warnings qw/recursion/;
    my ($n,$count) = @_;
    $count ||= 1;
    return $count + $cache{$n} if exists $cache{$n};
    if($n % 2){
      $cache{$n} = _three_n_plus_1(3*$n+1, $count+1) - $count;
      return $cache{$n} + $count;
    }else{
      $cache{$n} = _three_n_plus_1($n/2, $count+1) - $count;
      return $cache{$n} + $count;
    }
  }

  sub three_n_plus_1 {
    my ($i,$j) = @_;
    my $max = 0;
    for my $x ($i<$j ? $i..$j : $j..$i){
      my $t = _three_n_plus_1($x);
      $max = $t if $t > $max;
    }
    print "$i $j $max\n";
  }