package main

import (
	"fmt"
	"strings"
)

func main() {
	var n int
	var S, T string
	fmt.Scan(&n,&S,&T)
	s := strings.Split(S, "")
	t := strings.Split(T, "")
	ans :=0
	for i:=0; i<n; i++{
		if s[i]!=t[i]{
			ans ++
		}
	}
	fmt.Println(ans)
}