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

int main() {
  int n;
  cin >> n;
  string s, t;
  cin >> s >> t;
  int cnt = 0;
  for (int i = 0; i < n; ++i) if (s[i] != t[i]) cnt++;
  cout << cnt << endl;
}