#include <bits/stdc++.h>
#include <iostream>
using namespace std;

using ll = long long;
using pii = pair<int,int>;
using vi = vector<int>;

#define fastio ios::sync_with_stdio(false); cin.tie(nullptr);
#define all(x) (x).begin(), (x).end()

int main() {
    fastio;
    int n ;
    cin >>n ;
    string a , b ;

    cin >> a ;
    cin >> b ;
    int total = 0;

    for (int i = 0; i < n; i++) {
        if(a[i]!=b[i])    total ++;

    }

    cout << total;




    return 0;
}