#include <iostream>
using namespace std;
int main(void){
    // Your code here!
    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;
}