// No.224 文字列変更(easy)
package main

import (
	"fmt"
)

func main() {
	var n int
	var s, t string
	fmt.Scan(&n, &s, &t)

	ans := 0
	for i := 0; i < n; i++ {
		if s[i] != t[i] {
			ans++
		}
	}
	fmt.Println(ans)
}