#include<iostream>
#include<string>
using namespace std;
int main()
{
    int N;
    string S,T;
    cin>>N>>S>>T;
    int cnt_differ = 0;
    for(int i=0;i<S.length();i++){
        if(S[i] != T[i])cnt_differ++;
    }
    cout<<cnt_differ<<endl;
    return 0;
}