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

int main() {
    int n,ans = 0;
    string s,t;
    cin >> n >> s >> t;
    for(int i = 0;i < n;i++){
        if(s[i] != t[i])ans++;
    }
    cout << ans << endl;
    return 0;
}