#include <iostream>
#include <string>
#include <cstring>
#include <vector>

using namespace std;

int main()
{
	int N;
	cin >> N;

	string S;
	string T;
	cin >> S;
	cin >> T;
	int cnt = 0;
	for( int i = 0; i < N; i++ ) {
		if( S[i] == T[i] ) {
		}
		else {
			cnt++;
		}
	}
	cout << cnt << endl;

	return 0;


}