#include <bits/stdc++.h>
#define int long long
using namespace std;
using Graph = vector<vector<int>>;

signed main(){
  int N;
  cin >> N;
  string S, T;
  cin >> S >> T;
  
  int ans = 0;
  for( int i = 0; i < N; i++ ){
    if( S.at(i) != T.at(i) ) ans++;
  }
  cout << ans << endl;
}