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

void solve() {
    int n;
    cin >> n;
    string s, t;
    cin >> s >> t;
    
    int ans = 0;
    for(int i = 0; i < n; i++) {
        if(s[i] != t[i]) ans++;
    }
    cout << ans << "\n";
}

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    solve();
    return 0;
}