#include <bits/stdc++.h>

#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define rrep(i, n) for(int i = ((int)(n)-1); i >= 0; i--)
#define all(x) (x).begin(),(x).end()
#define pb emplace_back

using namespace std;
using ll = long long;

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> P;
 
const int INF = 1e9;
const double EPS = 1e-10;
const int MOD = 1e9+7;
const double PI = acos(-1.0);

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