#!/usr/bin/perl -wT
use strict;

my $base36 = shift;
$base36 = 10 if !defined $base36;
die "invalid input, only 0-9 and A-Z allowed\n"
    if $base36 !~ /^[0-9A-Z]+\z/;

my $dec = base36($base36);

print "$base36 => $dec\n";

sub base36 {
  #        1         2         3         4         5         6
  #234567890123456789012345678901234567890123456789012345678901
  $%+=$_*36**$?++for reverse map/\d/?$_:ord($_)-55,pop=~/./g;$%
}