#!/usr/bin/perl -w

use strict;
use constant BLACK_THRESHOLD => 16;

# Parse header.
my ($magic, $size, $depth);
defined($magic = <>) or die;
defined($size = <>) or die;
defined($depth = <>) or die;
die unless $magic =~ /^P5/ && $depth =~ /^255/ && $size =~ /^(\d+) (\d+)/;
my $width = $1;
my $height = $2;

# Output bytes.
my $data = join '', <>;
length($data) == $width * $height or die;

for(my $y = 0; $y < $height; $y++)
{
   foreach my $c (unpack 'C*', substr($data, $y * $width, $width))
   {
      if( $c < BLACK_THRESHOLD )
      {
         print " ";
      }
      else
      {
         my $level = int(25 * ($c - BLACK_THRESHOLD) / (255 - BLACK_THRESHOLD));
         print chr(65 + $level);
         #print "X";
      }
   }
   print "\n";
}