#include <bits/stdc++.h>

int main() {

  int n;
  std::string s;
  std::string t;
  int ans = 0;

  std::cin >> n >> s >> t;

  for(int i = 0; i < n; ++i) {
    if( s[i] != t[i] ) {
      ans += 1;
    }
  }

  std::cout << ans << std::endl;

  return 0;
}