use bigint;
while(<>) {
    my ($a, $b)= split/ /;
    $a += 0;
    print $a - $b, "\n";
}

##</code><code>##

use bigint;
while(<>) {
    my ($a, $b)= map { 0+$_ } split/ /;
    print $a - $b, "\n";
}