#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <algorithm>
#include <iostream>
#include <utility>
#include <set>
#include <cctype>
#include <queue>
#include <stack>
#include <cstdio>
#include <cstdlib>
#include <cmath>
using namespace std;
string a,b;
int main(){
	int n;
	int res =0;
	while(cin>>n){
		cin>>a>>b;
		for(int i=0;i<n;++i){
			if(a[i] != b[i]){
			++res;
			}
		
		}
	}
	cout<<res<<endl;
	return 0;
}