#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001


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