#!/usr/bin/perl -w

use strict;

my $blocklen;
my $bitlen;
my $maxN;

if (@ARGV < 1) {
  print "Usage: $0 <bitlen> <files...>\n";
  exit 1;
}

$bitlen = shift;
$maxN = 2 ** $bitlen - 1;
$blocklen = int(log($maxN)/log(10.0) / 3.0);

#$bitlen = -1;

my $cnt = 0;
my $x = "";

while (<>) {
  chop;
  my $s = $_;
  if ($bitlen == -1) {
    $blocklen = int( (length($s)+2) / 3);
  }
  if (length($s) > $blocklen*3) {
    print("Illegal format in line $. \n");
    exit(1);
  }
  my $zeros = "0" x ($blocklen*3);
  $s = substr "$zeros$s", -$blocklen*3;
  for ($cnt = 0; $cnt < $blocklen; $cnt++) {
    my $y = substr $s, 0, 3;
    $s = substr $s, 3;
    my $adds = chr($y);
    $x = "$x$adds";
  }
}
$x =~ s/ *$//;
print "$x";