// No.224 文字列変更(easy)
// https://yukicoder.me/problems/no/224
//

#include <iostream>
#include <string>
using namespace std;

int solve(string &S, string &T);

int main() {
    int n;
    cin >> n;
    string S, T;
    cin >> S;
    cin >> T;
    
    int ans = solve(S, T);
    cout << ans << endl;
}

int solve(string &S, string &T) {
    int ans = 0;
    for (size_t i = 0; i < S.size(); i++) {
        if (S[i] != T[i])
            ans++;
    }
    return ans;
}