#include <bits/stdc++.h>
using namespace std;

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

	int ans = 0;
	for( int i = 0; i < N; i++ ) {
		if( S[i] != T[i] ) ans++;
	}

	cout << ans << endl;
}