package main

import (
	"fmt"
)

var (
	n int
	S string
	T string
)

func resolve() int {
	ret := 0
	for i := 0; i < n; i++ {
		if S[i] != T[i] {
			ret += 1
		}
	}
	return ret
}

func main() {
	fmt.Scanf("%d\n", &n)
	fmt.Scanf("%s\n", &S)
	fmt.Scanf("%s\n", &T)
	fmt.Println(resolve())
}