#include<bits/stdc++.h>
#define rep(i,a,n) for (int i = a;i < n;i++)
#define per(i,n,a) for (int i = n-1;i >= a;i--)
using namespace std;

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