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

int n;
string S, T;

int main() {
  while (cin >> n) {
    cin >> S >> T;
    int res = 0;
    for (int i = 0; i < n; ++i) {
      if (S[i] != T[i]) ++res;
    }
    cout << res << endl;
  }
}