#include <iostream>
#include <string>
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)

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