#include <stdio.h>

int main(){
	int val = 0;
	scanf("%d",&val);
	
	char str1[val], str2[val];
	scanf("%s%s",str1,str2);
	
	int count = 0;
	for(int i = 0;i < val;i++){
		if(str1[i] != str2[i]){
			count++;
		}
	}
	printf("%d",count);
}