<?php
$n = trim(fgets(STDIN));
$moji1 = str_split(trim(fgets(STDIN)));
$moji2 = str_split(trim(fgets(STDIN)));
$count = 0;
foreach ($moji1 as $key => $value) {
    if ($moji1[$key] !== $moji2[$key]) {
        $count ++;
    }
}
echo $count;