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

int max(int a, int b) {
	int x = (a > b) ? a : b;
	return x;
}

int min(int a, int b) {
	int x = (a < b) ? a : b;
	return x;
}

int binary_search(int n, vector<int> v,int key) {
	int left=0, right=n;

	while (left < right) {
		int mid = (left + right) / 2;
		if (v[mid] == key) return mid;
		else if (v[mid] < key) {
			left = mid + 1;
		}
		else if (v[mid] > key) {
			right = mid - 1;
		}
	}
}

int main() {
	int n;
	cin >> n;
	string s, ss;
	cin >> s >> ss;

	int count = 0;
	for (int i = 0; i < s.length(); i++) {
		if (s[i] != ss[i]) {
			count++;
		}
	}
	cout << count << endl;

	return 0;
}