#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ul;
typedef signed long long ll;

int main(void)
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed;
  int n;
  string s, t;
  cin >> n >> s >> t;
  int ans = 0;
  for (int i = 0; i < n; ++i) {
    if (s[i] != t[i]) ans++;
  }
  cout << ans << endl;
  return 0;
}