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

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