use strict;
use warnings;

my $first = <DATA>;
chomp $first;
my $template = '';
while (<DATA>) {
    chomp;
    $template |= $first ^ $_;
}
for (split //, $template) {
    print ord == 0 ? '.' : 'X';
}
print "\n";

__DATA__
ATCG--ATCG-ATCG
ATGC--ATCG-ATCG
ATGC-A-TCG-ATCG
ATGC--ATCG-ATCG
ATCG--ATCG-AACG

##</code><code>##

..XX.XX.....X..