#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 7;

int main() {
    int n;
    cin >> n;
    
    string s, t;
    cin >> s >> t;

    int ans = 0;

    rep (i, s.length()) {
        ans += s[i] != t[i];
    }

    cout << ans << endl;
}