#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
using ll = long long;
using namespace std;
const int INF = 1e9;

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

    int cnt = 0;
    rep(i, n) if (s[i] != t[i]) {
        ++cnt;
    }

    cout << cnt << endl;

    return 0;
}