#include <iostream>
#include <string>
using namespace std;

#define rep(i, n) for (int i = 0; i < n; i++)
#define MAX 1000

int main()
{
	int n;
	string S, T;
	cin >> n >> S >> T;

	int ans = 0;
	rep(i, n)
	{
		if (S[i] != T[i])
		{
			ans++;
		}
	}
	cout << ans << endl;
}