#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;
using ld=long double;
using vll=vector<ll>;
using pll=pair<ll,ll>;

using mint=modint;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

    ll n,m=0;
    string S,T;
    cin>>n>>S>>T;
    for(int i=0;i<n;++i){
        if(S[i]!=T[i])m++;
    }
    cout<<m<<endl;
}