#include <bits/stdc++.h>
#define rep(i, ss, ee) for (int i = ss; i < ee; ++i)
using namespace std;

int solve() {
  int N, ans = 0;
  string s, t;
  cin >> N >> s >> t;
  rep(i, 0, N) if (s[i] != t[i]) ans++;
  return ans;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << solve() << endl;
  getchar();
}