#include <bits/stdc++.h>

using namespace std;
typedef long long ll;


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

    return 0;
}