text: #include<bits/stdc++.h>
  using namespace std ;
  
  int go(string& brides, string& grooms){
      int answer = 0 ;
      for(auto &&x : brides){
          auto f = grooms.find_first_of(x) ;
          if(f != string::npos) {
              grooms.erase(f, 1) ;
          }
      }
      return answer =  grooms.size() ;
  }
  
  int main(int argc, char const *argv[]){
         
      int n ;
      cin >> n ;
      string brides , grooms ;
      cin >> brides >> grooms ;
  
      cout << go(brides, grooms) << endl ;
  
      return 0;
  }
  