#include<bits/stdc++.h>
#define ll long long
using namespace std;
int qf(int x){
	if(x==1)
		return x--;
	return x++;
}
int a[114514],b[114514];
string s1,s2;
int main(){
	int n;
	cin>>n;
	cin>>s1>>s2;
	for (int i=0;i<n;i++){
		a[i]=int(s1[i]);
		b[i]=int(s2[i]);
	}
	sort(a,a+n);
	sort(b,b+n);
	/*for (int i=0;i<n;i++){
		cout<<char(a[i]);
	}
	cout<<endl;
	for (int i=0;i<s1.length();i++){
		cout<<char(b[i]);
	}*/
	int ans=0;
	for (int i=1;i<=n;i++){
		if(a[i]!=b[i]){
			ans++;
		}
	}
	cout<<ans<<endl;
}