#include <iostream>
#include <vector>
#include <string>

#define REP(i, a, b) for (int i = (a); i < (b); i++)
#define dump(s) cerr << __LINE__ << "\t:" << #s << " = " << (s) << endl
    
using namespace std;

int main () {
    int n;
    cin >> n;
    string s, t;
    cin >> s >> t;
    int ans = 0;
    REP (i, 0, n) {
	ans += (s[i] != t[i]);
    }
    cout << ans << endl;
    
    return 0;
}