#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)

int main(void)
{
  int n;
  cin >> n;
  string s, t;
  cin >> s >> t;

  int ans = 0;
  rep(i, n) if (s[i] != t[i]) ans++;

  cout << ans << endl;
  return 0;
}