#include <stdio.h>
#include <stdlib.h>

int main()
{
	int n, failure = 0;

	scanf("%d", &n);

	char* S, * T;
	S = (char*)malloc(sizeof(char) * n);
	T = (char*)malloc(sizeof(char) * n);

	scanf("%s", S);
	scanf("%s", T);

	for (int i = 0; i < n; i++)
	{
		if (S[i] == T[i])
		{
			continue;
		}

		failure++;
	}

	printf("%d", failure);

	return 0;
}