#include <bits/stdc++.h>
using namespace std;
int main(){
  int n;
  cin >> n;
  string S;
  cin >> S;
  string T;
  cin >> T;
  int ans = 0;
  for (int i = 0; i < n; i++){
    if (S[i] != T[i]){
      ans++;
    }
  }
  cout << ans << endl;
}