#include <iostream>
#include <string>
using namespace std;
int main()
{
	short n,a=0;
	string S, T;
	cin >> n;
	S.resize(n);
	T.resize(n);
	cin >> S >> T;
	for (short i = 0; i < n; i++)
	{
		if (S[i] != T[i]) a++;
	}
	cout << a << endl;
	return 0;
}