#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <utility>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <deque>
#include <cmath>
#include <numeric>
#include <bitset>
#include <cstring>
#include <array>
#include <list>
using namespace std;

#define ll long long
#define vi vector<int>
#define vll vector<ll>
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define ff first
#define ss second



void solve() {
    int n; cin>>n;
    string a; cin>>a;
    string b; cin>>b;
    int count = 0;
    for(int i=0;i<a.size();i++){
        if(a[i]!=b[i]) count++;
    }
    cout<<count<<endl;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    
    int t = 1;
    //cin >> t;
    while(t--) {
        solve();
    }
    return 0;
}