#include <stdio.h>

int main(void){
	int diff=0;
	int i,n;
	char s[1100], t[1100];
	scanf("%d", &n);
	scanf("%s", s);
	scanf("%s", t);
	
	for(i=0;i<n;i++){
		if(s[i] != t[i]){
			diff++;
		}
	}
	printf("%d\n", diff);
	return 0;
}