#!/usr/bin/env perl
use strict;
use warnings;

my %sequences = (
 I   => 'CATCAGTATAAAATGACTAGTAGCTAGATACCACAGATACGATACAACA',
 II  => 'TACCACAGATACGATACAACACATCAGTATAAAATGACTAGTAGCAGAC',
);

while (<DATA>) {
  my @f = split(/\s+/, $_);
  substr ($sequences{$f[0]},$f[1]-1,1) = $f[3];
}

print "CGTTGGCATAAAATGACTAGTAGCTAGATACCACAGATACGATACAACA\n";
for my $key (keys %sequences){
  print $sequences{$key}."\n";
}
__DATA__
I	2	A	G
I	4	C	T
I	5	A	G
I	7	T	C
II	1	T	C
II	2	A	G
II	3	C	T
II	5	A	C
II	8	G	T
II	10	T	G