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

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

    int ans = 0;
    for(int i = 0; i < n; i++)
        if(s[i] != t[i]) ans++;

    cout << ans << endl;

    return 0;
}