#include<iostream>
#include<string>

#define rep(i,n) for(i=0; i<n; i++)

using namespace std;

int main()
{
    int n;
    cin >> n;
    string s1, s2;
    cin >> s1 >> s2;
    
    int i,cnt=0;
    rep(i,n) {
        if(s1[i] != s2[i]) { cnt++; }
        else {continue;}
    }
    cout << cnt << endl;
    return 0;
}