#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <cmath>
#include <climits>
#include <iomanip>
#include <set>
#include <map>
using namespace std;
typedef long long ll;
int main(){
    ll n;
    cin >> n;
    string a,b;
    cin >> a >> b;
    ll res = 0;
    for(int i = 0;i < n;i++){
        if(a[i] != b[i])res++;
    }
    cout << res << endl;
}