use warnings;
use strict;

my $mask_input = '0000000000';
my %intervals = ( 0, ( do { local $/; <DATA> } =~ /(\d+)/g ), 1+length $mask_input );

while( my( $start, $end ) = each %intervals ) {
		substr( $mask_input, $start, $end-$start-1 ) =~ tr/N/N/c;
}

print "$mask_input\n";

__DATA__
chrX      1      3
chrX      5      6
chrX      8      9