#include <stdio.h>

int main(void)
{
	int n, i = 0, u = 0;
	char s[1001], t[1001];
	scanf("%d\n%s\n%s", &n, s, t);
	for (i; i < n; i++) s[i] == t[i] ? u : u++;
	printf("%d\n", u);
	return 0;
}