#! /usr/local/bin/perl
use IO::File;
for ( $k=0 ; $k<=$#ARGV ; $k++ ) {
    $F[$k] = new IO::File "<$ARGV[$k]"
	or die "Can't open $ARGV[$k]\n";
}
for ( $i=0 ; $i<128*1024 ; $i++ ) {
    $byte = 0;
    for ( $k=0 ; $k<=$#ARGV ; $k++ ) {
	$b = "\000" unless ((read ($F[$k], $b, 1)) or 0)==1;
	$byte ^= unpack "C", $b;
    }
    print (pack "C", $byte);
}
