#include<stdio.h>

int main(void){
	int n,i,r=0;
	char s[1024],t[1024];
	scanf("%d%s%s",&n,s,t);
	for(i = 0;i < n;i++){if(s[i]!=t[i]){r++;}}
	printf("%d\n",r);
	return 0;
}