#include <iostream>
#include<string>

using namespace std;

int main(){
	int n,count=0;
	string str1,str2;

	cin>>n;
	cin>>str1;
	cin>>str2;

for (int i = 0; i < n; ++i)
{
	if(str1[i]!=str2[i]){
		count++;
	}
}
	cout<<count<<endl;
}