#include <stdio.h>
#include <algorithm>
#include <deque>
using namespace std;
using ll = long long;

//224
int main() {
	int n, diff = 0;
	char s[1001], t[1001];
	scanf("%d %s %s", &n, s, t);

	for (int i = 0; i < n; i++)
		diff += s[i] != t[i];
	printf("%d\n", diff);
}