#include <stdio.h>

int main(void) {
	int i, n, count;
	char S[1001], T[1001];
	scanf("%d", &n);
	scanf("%s", S);
	scanf("%s", T);
	count = 0;
	for(i = 0;i < n;i++){
		if(S[i] != T[i]){
			T[i] = S[i];
			count++;
		}
	}
	printf("%d\n", count);
	
	return 0;
}