#!/usr/bin/env perl

use strict;
use warnings;

my $n = <>;
my $s = <>;
my $t = <>;
chomp $s;
chomp $t;
my @S = split //, $s;
my @T= split //, $t;

my $res = 0;
for(my $i = 0; $i < $n; $i++) {
	if($S[$i] ne $T[$i]) {
		$res++;
	}
}

print "$res\n";

exit;