#!/usr/bin/perl -w

use strict;

#             0   4   1   5   3   2
my @values = (21, 25, 15, 12, 52, 51);

for(my $mod = 6; $mod < 10; $mod++)
{
   for(my $shift = 0; $shift < 10; $shift++)
   {
      my @outputs = ();
      push @outputs, 0 foreach @values;
      my $accepted_outputs = 0;

      foreach (@values)
      {
         my $mapped_value = ($_ + $shift) % $mod;
         last if $mapped_value < 0 || $mapped_value >= (scalar @values);
         last if $outputs[$mapped_value];
         $outputs[$mapped_value] = 1;
         $accepted_outputs++;
      }

      if( $accepted_outputs == (scalar @values) )
      {
         print "mod=$mod, shift=$shift\n";
      }
   }
}