//#include <atcoder/all>
#include<bits/stdc++.h>
using namespace std;
//using namespace atcoder;
using ll = long long;
#define all(A) A.begin(),A.end()
using vll = vector<ll>;
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
using Graph = vector<vector<ll>>;
vector<ll> fact, factinv, inv;


int main() {
   ll N,an=0;
   string S,T;
   cin>>N>>S>>T;
   rep(i,N){
       an+=(S[i]!=T[i]);
   }
   cout<<an<<endl;

}