#include <bits/stdc++.h>

using namespace std;

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

  int ans = 0;
  for (int i = 0; i < n; i++) {
    ans += s[i] != t[i];
  }

  cout << ans << endl;

  return 0;
}