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

int main(){


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