#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>
using namespace std;
typedef pair<int, int> pii;
#define rep(i,x) for(int i=0;i<(int)(x);++i)

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