#include <bits/stdc++.h>

using namespace std;

int main()
{
  int n;
  string S, T;

  cin >> n;
  cin >> S;
  cin >> T;
  
  int ret = 0;
  for(int i = 0; i < S.size(); i++) {
    ret += S[i] != T[i];
  }
  cout << ret << endl;
}