#!/usr/bin/perl
        
use strict;  
use warnings;
    
while (<DATA>) {
    chomp;   
    my ($f, $s) = split;
    unless (length ($f) == length ($s)) {
        print "$f-$s\n";
        next;
    }   
    if ($f == $s) {
        print $f, "\n";
        next;
    }  
    print "$f-", substr ($s => length +(("$f" ^ "$s") =~ /^(\x00*)/) [0]), "\n";
}

__DATA__
1   32
4   19
28  39
34  123
321 321
324 329
325 349      
340 509