#include
 using namespace std;
 #include
 int has1[26],has2[26];
  int main()
   {
    int n;
      cin>>n;
        char ff[n+10],ss[n+10];
          for(int i=0;i>ff[i];
               has1[ff[i]-'a']++;
          }
            for(int i=0;i>ss[i];
                  has2[ss[i]-'a']++;
            }
            sort(ff,ff+n/2);
              sort(ss,ss+n/2);
              //case 1
               int ans1=0,ans2=0,ans3=0;
              for(int i=0;i<26;i++)
              {
                  ans1+=abs(has1[i]-has2[i]);
                //    cout<<"i " <